Clinical Consequences of Enzyme Deficiencies in the Erythrocyte

Home , Enolase deficiency, Hexokinase deficiency

MICHAEL L. NETZLOFF, M.D.

Department of Pediatrics and Human Development, Michigan State University College of Human Medicine, East Lansing, Ml 48824

ABSTRACT

The anueleate mature erythrocyte also lacks ribosomes and mitochondria and thus cannot synthesize enzymes or derive energy from the Krebs citric acid cycle. Nevertheless, the red blood cell is metabolically active and contains numerous residual enzymes and their products which are essential for its survival and normal functioning. Enzyme deficiencies in the Embden-Myerhoff glycolytic pathway can result in nonspherocytic hemoly tic anemia (NSHA), and some are also associated with neuromuscular or neurologic disorders. Glucose-6-phosphate dehydrogenase deficiency in the hexose monophosphate shunt also results in hemolytic anemia, espe cially following exposure to various drugs. Defects in glutathione synthesis and pyrimidine 5'-nucleotidase deficiency also cause NSHA, as does in creased adenosine deaminase activity. Glutathione synthetase deficiency which is not limited to the red cell also presents as oxoprolinuria with neurologic signs. All red cell enzyme defects appear as single gene errors, in most cases recessive in inheritance, either autosomal or X-linked.

Clinical Consequences of Enzyme tains over 40 different enzymes, many of Deficiencies in the Erythrocyte which are essential for its survival or nor mal functioning. The purpose of this re Prior to maturity, the nucleated red port is to review some inherited enzyme blood cell (rbc) can perform a variety of deficiencies of the erythrocyte which metabolic functions, including active en compromise its viability in the circulation zyme synthesis. The mature erythrocyte or its capacity to transport oxygen, result has no nucleus or ribosomal apparatus, ing in clinical disease. and thus cannot synthesize protein. How ever, it is not metabolically inert and con- Red Blood Cell Metabolism

Reprinted requests to: Michael L. Netzloff, M.D., In addition to the metabolic restrictions Department of Pediatrics and Human Development, B-240 Life Sciences, Michigan State University, on the mature erythrocyte previously East Lansing, MI 48824. noted, its energy sources are also some 414 0091-7370/80/0900-0414 $01.80 © Institute for Clinical Science, Inc. SIGNS OF RED CELL ENZYME DEFICIENCIES 415 what limited by the loss of its mitochon H M P may be used in the synthesis of nuc dria. Without these organelles, the rbc leotides or rearranged to the 3-and cannot metabolize pyruvate through the 6-carbon sugars used in glycolysis for Krebs citric acid cycle. Other energy sub production of additional 2,3-DPG and strates can be used by the red cell, but the ATP. major source is normally glucose through Some common hereditary diseases of either the Embden-Meyerhoff or hexose the rbc which involve alterations in shape monophosphate pathways. The energy (e.g., spherocytosis, elliptocytosis, etc.) thus derived has several essential uses:3,24 are likely membrane defects and may in (1) the m aintenance of sodium and potas volve enzyme deficiencies not yet iden sium gradients across the cell membrane; tified.24 This review will be limited to (2) the prevention of calcium accumula known enzyme deficiency states, many of tion in the red cell membrane; (3) mainte which cause nonspherocytic hemolytic nance of the integrity and shape of the rbc anemia. m em brane; (4) reduction of m ethem oglo- bin and oxidized gluthathione; (5) inacti Red Blood Cells Enzyme Deficiencies vation of peroxides and other oxidants in the Embden-Meyerhoff Pathway which denature hemoglobin; and (6) P y r u v a t e K i n a s e D e f i c i e n c y maintenance of levels of organic phos phates, e.g., 2,3 diphosphoglycerate Although the recognition of non (2,3-DPG) and adenosine triphosphate spherocytic hemolytic anemia (NSHA) (ATP), affecting hemoglobin-oxygen was made as recently as 1953, it was not affinity. until 1961 that Valentine et al32 discov The energy derived from the ered pyruvate kinase (PK) deficiency, the Embden-Meyerhoff glycolytic pathway is most common cause of NSHA. PK defi primarily stored in the high energy phos ciency is second to glucose-6-phosphate phate of ATP. The latter is used to drive dehydrogenase (G-6-PD) deficiency as the sodium and potassium pumping sys the most common inherited rbc enzyme tems which oppose the passive diffusion defect and is an autosomal recessive dis of these ions and water across the cell order. Although it has been suggested that membrane. If unopposed, these natural heterozygotes may infrequently have processes would result in eventual clinical findings, most of these examples hemolysis. Anaerobic glycolysis also gen are confounded by the simultaneous oc erates reducing power by converting currence of other hemolytic disorders.3 nicotinamide adenine dinucleotide Large numbers of heterozygotes have (NAD+) to NADH, which reduces been found to have no hemolytic disease, methemoglobin to hemoglobin. Synthesis and it is doubtful that the heterozygous of 2,3-DPG also occurs in the glycolytic condition itself causes hemolysis.3 pathway. Considerable heterogeneity in bio Normally, the hexose monophosphate chemical properties of mutant PK enzymes pathway (HMP) accounts for only 10 per has been observed and may explain cent of the glucose metabolism of the red the marked variation in hemolysis and cell.3 This percentage is greatly increased anemia in affected patients. Disease oc during oxidative stress with the produc curs in true homozygotes who have inher tion of NADP+ from NADPH. The HMP ited two identical mutant alleles, as well maintains this conversion in favor of as in double heterozygotes, or genetic NADPH, which keeps gluthathione in its compounds, with two different mutant al reduced form, in turn protecting the rbc leles affecting different parts of the PK from peroxidation. Pentose formed in the enzyme. The latter condition could give 416 NETZLOFF rise to two different abnormal amino acid Earlier studies and those recently re substitutions with the formation of two ported by Bowman and Oski5 have variant enzymes or their hybrid enzyme. suggested that the spleen is the first organ Since PK is known to be an allosteric en to trap and destroy susceptible PK defi zyme affected by fructose diphosphate cient red cells, principally reticulocytes. with marked pH dependency, a mutant These observations help to explain the re- allele might result in enzyme products ticulocytosis which occurs in all red cell with modifications of either the catalytic PK-deficient patients after splenectomy. or the allosteric site. Gherardi et al11 has When the spleen is present, its low oxy recently reported data on a family suggest gen tensions prevent mitochondrial ATP ing an alteration of the PK allosteric site. production in reticulocytes both in normal In addition to the hereditary PK defi and PK-deficient patients. The later ciency, the enzyme defect can be caused would also suffer from impaired by a wide variety of hematologic disor glycolysis, with further reduction of avail ders.3 These include, most commonly, able ATP. The ATP-dependent cation acute leukemia, as well as cytopenias, pump appears defective in red cells from anemias, and aplasias. The acquired vs. such patients, and this might affect the hereditary forms of PK deficiency can be external calcium pump and cause inter differentiated by observing the return of membrane calcium concentration, induc enzym e activity to norm al once the u nder ing membrane ridigity. This sequence lying disorder is treated, or by family could be the pathogenesis of the abnormal studies. The latter rely on the facts that cell morphology21 and deformability22 parents of patients with hereditary PK de reported in erythrocyte populations in ficiency are obligate heterozygotes with PK-deficiency anemia following diminished enzyme levels intermediate splenectomy. between normal and affected, and sib Because of the biochemical hetero lings of patients with hereditary PK defi geneity of PK-deficiency, variability of ciency may also have demonstrable PK clinical expression is expected.3 Anemia disorders. may be so severe that multiple transfu Since some investigators have reported sions or splenectomy is life-saving, or the no relationship between in vitro proper patient may remain asymptomatic for ties of variant PK enzymes and the sever years. Other signs are also not distinctive ity of hemolysis, the hypothesis has been for PK-deficiency disease. Patients may advanced that hemolysis in PK deficient have jaundice, bilirubinuria, splenome red cells is caused by another defect in the galy, and sometimes gallstones. Jaundice cell membrane.36 However, interpretation usually presents in the neonatal period of biochemical results is hampered by and kernicterus has been reported and can several factors. First, inheritance of two be fatal. Hemolysis increases during in different mutant alleles allows formation tercurrent infection and following use of of five different types of the tetramer en oral contraceptives.18 PK-deficiency is a zyme. Also, studies utilizing crude cause of failure to thrive in severely af hemolysates are hampered by the actions fected children. Radiographs show the of other enzymes, and purification of PK changes secondary to a hypertrophic bone itself can change its kinetic properties. marrow seen during any severe anemia. Failure to remove contaminating leuko Diagnosis of frank decreases of PK ac cytes results in the measurement of their tivity can be made biochemically using a PK enzymes, which are neither deficient coupled reaction in which the product, nor of the same type as the red cell en pyruvate, oxidizes NADH to NAD+ in the zyme in PK deficiency. lactate dehydrogenase reaction. Trials SIGNS OF RED CELL ENZYME DEFICIENCIES 4 1 7 with various therapies such as steroids, H e x o k in a s e D e f i c i e n c y AMP, magnesium, and riboflavin have been disappointing; blood transfusions Hexokinase deficiency is a rare cause of and splenectomy are the currently effec NSHA and is inherited as an autosomal tive modes of therapy.3 recessive disorder. Although heterozy gotes have approximately half the normal enzyme activity, similar levels are fre quently seen in hexokinase-deficient pa G l u c o s e P h o s p h a t e I s o m e r a s e tients. This observation can be explained D e f i c i e n c y by the marked decrease in levels of this The conversion of glucose-6-phosphate enzyme with aging of the normal red cell. to fructose-6-phosphate via glucose phos With reticulocytosis, the larger popula phate isomerase (GPI) is the second step tion of younger cells containing more en of the Embden-Meyerhoff pathway. Defi zyme in the deficient variants masks the ciency of GPI is one of the more common true extent of the enzyme reduction. This identifiable causes of NSHA, probably finding also complicates the chemical third in frequency to G-6-PD-and PK- demonstration of hexokinase deficiency, deficiencies. Like PK deficiency, GPI- but the diagnosis can be made if hexo deficiency anemia is an autosomal reces kinase is compared to other age-de sive disorder and was not reported until pendent enzymes such as PK and relatively recently, (1968).1 Since that G-6-PD.3 time numerous examples have been re Clinical manifestations of hexokinase ported in diverse population groups. The deficiency are those of NSHA. Symptoms enzyme appears to occur in dimer form of anemia may be more severe than the and, unlike PK, GPI isozymes from differ anemia alone would suggest because of ent tissues have similar electrophoretic the associated low 2,3-DPG levels, which properties and are also deficient when the further compromise oxygen delivery. In red cell enzyme is decreased. Diminished addition, easy fatigability upon physical deformability of GPI-deficient red cells exertion and muscle hypertrophy in the has recently been reported, and the distal extremities with glycogen deposi suggestion made that this prediposes tion has been reported in two sisters with them to splenic sequestration.26 hexokinase deficiency.12 The diversity of deficient and nondefi Experience with treatment is limited to cient variants of GPI isozymes among the few patients discovered to date, but people may explain the continuum of sev splenectomy has been effective. erity of clinical disease. Anemia may be mild, or may require frequent transfusions P hosphofructokinase D e f i c i e n c y and splenectomy. Symptoms and signs re ferable to NSHA are com m only observed; The third step of the Embden-Meyer only rarely have other features such as hoff pathway is the phosphorylation of mental retardation, increased blood vis fructose-6-phosphate to fructose-1,6- cosity, and increased liver glycogen been disphosphate catalyzed by phospho reported.3 None of these features are fructokinase (PFK). This reaction pro characteristic of GPI-deficiency, and ceeds in the forward direction almost diagnosis requires assay of enzyme activ exclusively and is a key point of regulation ity. Effective management of these pa of glycolysis. PFK deficiency shows auto tients is limited to splenectomy, and re somal recessive inheritance. sults have been almost universally Muscle PFK is deficient in type VII helpful.3 glycogen storage disease, a metabolic 4 1 8 NETZLOFF

myopathy characterized by easy fatigabil T r i o s e P h o s p h a t e I s o m e r a s e ity during childhood and subsequent D e f i c i e n c y severe muscle weakness and wasting, resembling type V (McArdle’s) disease. The dihydroxyacetone phosphate Patients with muscle PFK-deficiency dis formed in the aldolase-catalyzed step in ease have shortened red cell survival and glycolysis can undergo no further metabo may have clinical manifestations of lism in the red cell. Rather, it is converted NSHA. The latter has been observed in to GAP via triose phosphate isomerase patients with red cell PFK-deficiency (TPI). without muscle disease.17 These differ In addition to NSHA reported in pa ences in clinical expression may be ex tients with TPI deficiency, most patients plained by the additional rbc isozyme on manifest a severe neuromuscular dysfunc electrophoresis compared to the pattern tion with onset at age six months and for muscle, and differing biochemical death in childhood. Involved muscles in properties of red cell vs. muscle enzymes. clude flexors of the hips, knees and calves, Non-nucleated red cells may be more sen and pronators of the arms.3 In some, jaun sitive than nucleated muscle cells to the dice develops in the neonatal period, effects of mutational enzyme alterations. prior to death, or may be inapparent but Travis and Garvin,30 in a study using the with severe anemia developing at four to technique of discontinuous density gra five weeks of age. TPI-deficient children dient to separate younger from older red appear to be particularly prone to infec cells in neonates, showed increased labil tion, and the leukocyte count is frequently ity of PFK in older red cells, even when elevated. Phagocytosis by leukocytes is compared to the normal decline of PK ac normal when they are suspended in nor tivity with age. This suggests that the rela mal serum, and a slight decrease in the tive PFK deficiency in neonatal red cells number of B-lymphocytes has been re results from instability of an isozyme in ported.10 The neuromuscular deteriora newborns, possibly a fetal PFK. tion is progressive; elasticity, hypotonia, Splenectomy was apparently beneficial opisthotonos, muscle weakness, absent in a patient with PFK deficiency.3 limb reflexes, and hand tremors have been reported.3 Death in most patients re sults from respiratory impairment and re A l d o l a s e D e f i c i e n c y peated lower respiratory infections or sudden cardiac arrest. An enzyme assay Aldolase catalyzes the conversion of for TPI deficiency in the red cell hemolys- fructose-1, 6-disphosphate to two three- tate is diagnostic. carbon compounds, glyceraIdehde-3- Splenectomy did not benefit the one pa phosphate (GAP) and dihydroxyacetone tient in whom it was done. phosphate. A single patient with aldolase

deficiency has been reported.4 The pa G lyceradlehyde P h o s p h a t e tien t was th e product of a consanguineous D ehydrogenase D e f i c i e n c y mating, suggesting autosomal recessive inheritance. However, enzyme activity in The reversible reaction converting both parents was normal, suggesting that GAP to 1,3-diphosphoglycerate (1,3- the normal subunits in the multimeric en DPG) is catalyzed by glyceraldehyde zyme may have a stabilizing influence on phosphate dehydrogenase (GAPD), re the entire enzyme complex. quires inorganic phosphate, and converts The affected patient had moderate NAD+ to NAHD which is required for mental retardation, hepatic glycogen stor methemoglobin reduction. Partial defi age, and mild NSHA not requiring ciency of GAPD has b een reported in sev splenectomy. eral families, but the enzyme defect does SIGNS OF RED CELL ENZYME DEFICIENCIES 419 not seem to be related to hemolytic hibits DPGM activity, thus decreasing its anemia. own synthesis. Both acidosis and in creased amounts of ADP also decrease

P hosphoglycerate K in a s e 2.3-DPG synthesis by stimulating the D e f i c i e n c y PGK reaction. The enzymes DPGM, diphosphoglycerate phosphatase (DPGP), Two enzymes compete for 1,3-DPG as and monophosphoglycerate mutase a substrate. Phosphoglycerate kinase (MPGM) appear either to be identical (PGK) catalyzes its conversion to or to share the same enzyme proteins.3 3-phosphogly cerate, simultaneously Partial deficiencies of DPGM have generating ATP from adenosine diphos been described in three unrelated phate (ADP). Deficiency of PGK is inher families. Clinical manifestations range ited as a sex-linked disorder. Although from none, to a severe hemolytic anemia white cells are affected as well, leukocyte with death at age three months. Recently, function is normal. a clinically healthy 42-year-old-man was O nset of symptoms is generally early in described with complete deficiency of male hemizygotes and late in heterozy DPGM, suggesting either marked varia gous females.3 Almost all of the male pa bility in expression of the deficiency or tients show neurologic deficits. Moderate that another enzyme defect has occurred mental retardation and impaired learning in affected patients.25 are reported. In males, neonatal jaundice Despite sharing the same enzyme pro is often present. Anemia is variable, but teins, MPGM is normal in most patients reticulocytosis is a constant feature. Vari with reported DPGM deficiency, which able expression of the deficiency in can be detected spectophotometrically. females is explained by the Lyon hypothesis. Krietsch et al20 have recently D iphosphoglycerate P h o s p h a t a s e reported a large German kindred with D e f i c i e n c y PGK deficiency and no overt clinical Diphosphoglycerate phosphate (DPGP) signs. Diagnosis of male hemizygotes by catalyzes the dephosphorylation of spectrophotometric assay of the enzyme is 2.3-DPG to 3-PG. Jacobasch et al15 possible; heterozygotes have marked var studied two infants with retarded de iation of enzyme activity, as in other sex- velopment muscle hypertonia, light col linked disorders, so as to make this unreli ored hair, hyperlipidemia, cerebral able as a means of detecting all carriers. dysgenesis, and mild, compensated Three of four patients who underwent hemolysis. Red cell hemolysates from splenectomy appeared to benefit from the these infants did not release inorganic procedure. phosphate from 2,3-DPG, suggesting DPGP deficiency, although the actual en D iphosphoglycerate M u t a s e zyme activity was not measured. Addi D e f i c i e n c y tional patients with this syndrome have not been reported, and confirmation of the The second enzyme which competes postulated enzyme defect may be difficult for the substrate 1,3-DPG is diphospho because of the very low activity of DPGP glycerate mutase (DPGM), which trans in normal red cells. fers the 1-phosphate of 1-3-DPG to

3-phosphoglycerate (3-PGA) forming a E n o l a s e D e f i c i e n c y molecule each of 2,3-DPG and 3-PGA. This represents the only point in red cell Enolase catalyzes the dehydration reac metabolism where a net synthesis of 2,3- tion which forms phosphoenolypyruvate DPG occurs. The product 2,3-DPG in from 2-phosphoglycerate (2-PGA). A 420 NETZLOFF single case of hemolytic anemia following by ingestion of fava beans, and apparently exposure to nitrofurantoin and attributed spontaneously during the neonatal pe to enolase deficiency has been reported.28 riod. Heterozygote advantage with re No other cases of enolase deficiency ap gards to resistance to falciparum malaria pear in the literature, despite frequent has been demonstrated and may explain assay for this enzyme by reliable spectro- the high gene frequencies noted in some photometric technique. populations. Various nonhematologic diseases have Red Blood Cell Enzyme Deficiencies been associated with G-6-PD deficiency. in the Hexose Monophosphate Pathway These include increased seizure disor ders, cataracts, decreased risk of cancer, G l u c o s e -6 -P h o s p h a t e exhaustion of renin release stimulated by D ehydrogenase D e f i c i e n c y upright posture, and altered steroid me Glucose-6-phosphate formed in the tabolism, all of which remain uncom- hexokinase reaction may be oxidized by firmed.3 Mild chronic granulomatous dis G-6-PD to 6-phosphogluconolactone, the ease has been described in patients with first step in the hexose monophosphate less than one percent of normal G-6-PD shunt. NADPH which is converted from activity. NADP+ by the G-6-PD reaction is also a NSHA can occur spontaneously in pa strong inhibitor of the reaction, thus reg tients who usually have an unusual var ulating its own synthesis. NADPH is used iant G-6-PD, which deprives the red cell by the red cell to maintain glutathione in of virtually all of the enzyme activity.33 its reduced form, without which the red Presentation may be in the newborn pe cells suffers peroxidative damage. riod with jaundice requiring exchange The early recognition that exposure of transfusion. Anemia may be compensated susceptible individuals to certain drugs or not, and is markedly increased during such as the antimalarial, plasmoquine, intercurrent infection or by inappropriate caused hemolytic anemia lead to the dis drug administration. Mild jaundice and covery of red cell G-6-PD deficiency.7,34 splenomegaly is usually present. Het The development of electrophoretic erozygotes for these variants frequently techniques allowed preliminary separa have normal enzyme activity, since the tion of G-6-PD deficiencies into quite dif affected cells do not survive long in the ferent entities in Mediterranean vs. circulation, leaving mostly normal cells.3 American black populations. Diagnosis can be made by the G-6-PD deficiency is inherited by a glutathione stability test or by direct sex-linked mode, and it is estimated that measurement of enzyme activity. A fluo approximately 100 million people are en rescent spot screening test is available.2 zyme deficient, making it the most com Treatment includes avoidance of mon red cell enzyme deficiency.3 Fortu hemolytic drugs. The list of drugs elimi nately, the majority of such persons have nated should be sensible, and should not no clinical findings and are frequently un include medications such as aspirin, aware of their biochemical abnormality. which the patient knows from his own ex An astonishing number of distinct G-6-PD perience is innocuous.3 Nor should the variants has been discovered, and, with a patient be deprived the benefits of few exceptions noted for G-6-PD Mediter therapy with all sulfonamides since Gan- ranean, deficient people are not anemic trisin, for instance, is not hemolytic. Se under normal circumstances. Hemolysis vere hemolytic episodes may require may occur following exposure to certain transfusions. Response to splenectomy in drugs, by infections, by diabetic acidosis, these patients with NSHA has been vari SIGNS OF RED CELL ENZYME DEFICIENCIES 421 able, and genetic counseling may be use glutathione reductase deficiency are ac ful in this group of patients. tually due to nutritional riboflavin defi ciency,3 resulting in NSHA following ex 6 -P hosphogluconate posure to certain drugs or chemicals. D ehydrogenase D e f i c i e n c y These include many, if not all, of the drugs causing hemolysis in G-6-PD deficiency. The enzyme 6-phosphogluconate de Rarely, hereditary partial deficiency of hydrogenase (6-PGD) catalyzes the oxida glutathione reductase occurs apparently tion of 1-carbon from 6-phosphogluconate as a dominant disorder,23 but its associa to carbon dioxide, forming ribulose-5- tion with clinical disease is unproven. phosphate. Although hemolytic anemia has been associated with 6-PGD defi Glutathione Peroxidase Deficiency ciency, it is probably coincidental and red cell survival is shortened little, if at all, in A variety of environmental influences the 6-PGD-deficiency state.3 readily alter glutathione peroxidase (GSHPx) activity, including iron defi Defects in Glutathione Synthesis ciency and selenium deprivation, the lat ter because GSHPx is a selenium- The two sequential enzyme steps containing enzyme. GSPHx should pro which are potentially involved in heredi tect biological membranes from oxidative tary defective-glutathione synthesis are damage, but conflicting clinical reports those catalyzed by gammaglutamyl cys cast doubt on the cause-and-effect rela teine synthetase (GC-S) and glutathione tionship between decreased levels of this synthetase (GSH-S). Deficiency of either enzyme and hemolysis. An interesting ob enzyme can cause hemolytic anemia, and servation of red cell GSHPx deficiency in both deficiencies appear to be inherited patients with multiple sclerosis was re as autosomal recessive disorders.3 cently reported.27 The authors suggested a Generalized GSH-S deficiency results in correlation between the low content of oxoprolinuria, chronic metabolic acidosis selenium in forage and the high preva usually present in the neonatal period, lence of multiple sclerosis in certain geo and in some cases neurologic symptoms.13 graphic areas, an association as yet Other patients with what may be another unconfirmed. type of GSH-S deficiency only manifest symptoms of NSHA. Treatment of the lat Disorders of Nucleotide Metabolism ter includes avoidance of the same com pounds which produce hemolysis in P y r m id in e 5 '- N ucleotidase G-6-PD deficiency; splenecotomy has D e f i c i e n c y been beneficial. Vitamin E will prevent oxidant damage to GSH-S-deficient A hemolytic anemia characterized by leukocytes and improve their impaired marked basophilic strippling of ery capacity to kill bacteria.6 throcytes, and thought initially to be caused by ribose phosphate pyrophos- Glutathione Reductase Deficiency phokinase deficiency, was later shown to be due to pyrimidine-5'-nucleotidase Glutathione reductase functions during (PD-5'-N) deficiency.31 Inheritance is by aerobic metabolism in the red cell to an autosomal recessive mode, occurrence maintain reduced glutathione.8 Flavine among populations is widespread, and it adenine dinucleotide is the cofactor for is becoming one of the more common the reaction, and it is now apparent that known causes of NSHA. PD-5'-N defi the majority of cases reported as ciency also occurs as an acquired disease 4 2 2 NETZLOFF as a result of lead intoxication, in which it phosphate pathways, other redox enzyme is also the cause of the basophilic systems are effective. Catalase is one such stippling. enzyme whose function is the detoxifica Anemia due to PD-5'-N deficiency is tion of hydrogen peroxide (H20 2) pro usually mild and the age of onset is vari duced during normal metabolic pro able. Neonatal hyperbilumbineamia has cesses. In Japanese acatalasemia, addi been observed in this disease, and tion of excess H20 2 to a blood sample splenomegaly almost always occurs. results in the formation of methemoglobin. Harley et al14 have recently shown that However, patients with this disease have the high levels of uridine nucleotides almost normal ratios o f methemoglobin to which accumulate in this disorder are de hemoglobin, and only their increase in rived, at least partially, from biosynthetic Heinz body formation suggests suscepti pathways, rather than from degradative bility to the effects of oxidative stress.29 pathways alone. This suggests the possi One such probable manifestation is a ble effectiveness of treatment with in peculiar oral gangrene called Takahara’s hibitors of uridine kinase in this disorder. disease, suffered by about half of Of the routine therapies, splenectomy has acatalasemic children. Other than these produced variable improvement. occasional and intermittent oral lesions, patients are surprisingly free of symp I n c r e a s e d A d e n o s i n e D e a m in a s e toms. The presence of residual catalase A c t i v i t y enzyme in these patients, as well as mod estly increased GSHPx levels and signifi Decreased adenosine deaminase cantly increased superoxide dimutase ac (ADA) activity, which is associated with tivity, may help explain the comparatively combined immunodeficiency syndrome, benign clinical manifestations of this does not cause red cell abnormalities. On seeming biochemical disaster. the other hand, increased ADA function, inherited as an autosomal dominant dis order, causes mild anemia which may oc S u p e r o x i d e D i s m u t a s e D e f i c i e n c y casionally be completely compensated.3 Splenomegaly is present and the reticulo The superoxide free radical anion, Oi is cyte count is elevated in affected patients. converted by superoxide dismutase into ATP levels average 60 percent of normal Oi and H20 2. In the absence of superoxide dismutase, 0 2 reacts with H20 2 to produce controls and 50 percent of controls with increased reticulocytes. The increased hydroxyl radicals and singlet-excited oxy ADA activity may lower red cell ATP gen. All of these free radicals could dam levels by effectively shunting adenosine age chromosomes, producing increased from the adenosine kinase step which breaks and rearrangements which exceed normally produces adenine nucleotides. the DNA-repair capacity of the cell. Such chromosomal abnormalities occur in pa tients with Fanconi’s anemia, and Joenje Other Enzyme Activities of the et al16 have recently reported decreased Oxidation-Reduction System red cell superoxide dismutase activity in two unrelated patients with this disease. C a t a l a s e D e f i c i e n c y (A catalasemia ) Conclusion In addition to the protection from oxida The deficiency of some red cell en tive damage of red cells afforded by vari zymes, such as arginase,35 hypoxanthine- ous elements of the glycolytic and pentose guanine phosphoribosyl transferase,9 and SIGNS OF RED CELL ENZYME DEFICIENCIES 423 the virtually complete absence of an red blood cells. Ann. Clin. Lab. Sci. 8:23-29, isozyme of carbonic anhydrase19 in red 1978. 9. Fox, I. H.: Purine enzyme abnormalities: a four cells produce no obvious hematolgic con year experience. Adv. Exp. Med. Biol. sequences. Enzyme deficiencies involv 76A:265-269, 1979. ing the anaerobic and aerobic glycolytic 10. F r e y e o n , F ., L a u r a s , B ., and B o v i e r - L a p ie r r e , F .: Hereditary hemolytic anemia pathways frequently produce nonsphero- with triose phosphate isomerase deficiency. cytic hemolytic anemia. Pediatrie 30:55-65, 1975. A few of the enzyme deficiencies in 11. G h e r a r d i, M., Bie r m e , R., C o r b e r a n d , J., andVERGNES, H.: Heterogeneity of erythroc^j volved in Embden-Meyerhoff and pyruvate kinase deficiency and related meta glutathione synthetic pathways may also bolic disorders in patients with hematological produce neurologic disorders. diseases. Clin. Chim. Acta 78:465-471, 1977. 12. G o e b e l , K. M., G a s s e l , W. D ., G o e b e l , F. D ., The erythrocyte uses a complex, inter and K a f f a r n ik , H.: Hemolytic anemia and related series of reactions to produce ATP hexokinase deficiency associated with malfor and 2,3-DPG, and NADPH and NADH to mations. Klin. Wochenschr. 50:349-351, 1972. 13. H a g e n f e l d t , L., L a r s s o n , A., and A n d e r maintain the normal reduced state of s o n , R.: The y-glutamyl cycle and amino acid compounds which are being subjected to transport. New Eng. J. M ed.229:587-590, 1978. oxidative stresses. It is probably no coin 14. H a r l e y , E . H ., H e a t o n , A., and W ic o m b , W .: Pyrimidine metabolism in hereditary ery cidence that the red cell utilizes primarily throcyte pyrimidine 5' nucleotidase deficiency. a pathway which does not require oygen Metabolism 27:1743-1754, 1978. to derive its energy in order to complete 15. Ja c o b a s c h , G., Sy l l m -Ra p o p o r t , I., R o ig a s , H., and Ra p a p o r t , S.: 2,3-PGase-mangel als its role of oxygen transport. moegliche ursacha erhoehten APT-gehaltes. Clin. Chim. Acta 20:477-478, 1964. 16. J o e n j e , H., E r ik s s o n , A. W., F r a n t s , R. R., References and A r w e r t , F.: Erythrocyte superoxide- dismutase deficiency in Fanconi’s anemia. 1. Ba u g h a n , M. A., Va l e n t in e , W . N., P a g l ia , Lancet 2:204, 1978. D. E., W a y s , P. O., Sim o n , E. R., and D e - 17. Ka h n , A., E t i e m b l e , J., M e i e n h o f e r , M . C., M a r s h , Q . 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