Limiting Factors for Glycogen Storage in Tumors I. Limiting Enzymes *

Home , Cytidine diphosphate, Inosine, Purine, Uridine triphosphate

VIJA! N. NIGAM, HELEN L. MACDONALD,t AND A. CANTERO

(Montreal Cancer Institute, Research Laboratories, Notre Dame Ho8pital and UniveraW de Montreal, Montreal, Canada)

SUMMARY The paper presents a study of various enzymes involved in the final accumulation of glycogen in tumor tissues. The solid tumors used are : Novikoff hepatoma, Walker 256 carcinosarcoma, Sarcoma 37, leukemia, and melanoma. It was observed that tumor tissues showed lower activity of phosphoglucomutase and glycogen synthetase as compared with that of normal liver and muscle. All tumors studied except melanoma also showed decreased UDPG' pyrophosphorylase levels. Activities for ATP- and UTP-regenerating enzymesâ€”namely, pyruvate kinase and nucleoside disphospho kinaseâ€”in tumors were close to those found in normal tissues, thus providing sufficient quantities of cofactors (ATP and UTP) and energy for the polymerization process. UDPG was not diverted to UDPGA in tumors because of the absence of UDPG dehy drogenase. The lesion could be best described as a defective system for glycogen syn thesis, owing to low activities of the enzymes involved in the synthetic process (phos phoglucomutase and glycogen synthetase) which were unable to accomplish efficient transformation of G-6-P to G-1-P and of UDPG to glycogen, in the presence of com peting high rates of tumor glycolysis and normal polysaccharide degradation by phosphorylase.

The decreased content of glycogen, together perimental work, designed to explain the defi with high rates of glycolysis, has been observed in ciency of glycogen in tumor. most tumor tissues and reported extensively (1, The metabolic pathway through which glucose 11). Although a number of reports have appeared is finally converted to glycogen begins with its (1, 10, 12, 40) to explain the high rate of lactic phosphorylation to glucose-6-phosphate through acid production in tumors, the reasons for the lack hexokinase and adenosine triphosphate; next, its of glycogen accumulation have not been fully ex transformation to glucose 1-phosphate by phos plored. In the light of the new pathway for glyco phoglucomutase; and, fiuially, conversion of the gen synthesis mediated through uridine diphos glucose 1-phosphate to uridine diphosphate glu phate glucose, the problem is open for further ex cose in the presence of uridine triphosphate and UDPG-pyrophosphorylase (14).' The UDPG 5This work was supported by grants from the National Cancer Institute of Canada. formed can transfer its glucose moiety to a pre Presented at the meeting of American Society of Biological formed glycogen molecule through glycogen syn Chemists in Atlantic City, April 10, 1961. thetase (16), or it can undergo dehydrogenation to t Technical assistant. UDP-glucuronic acid (35) and later transfer the â€˜Theabbreviations used are: AMP, adenosine monophos glucuronic acid moiety to a suitable acceptor form phate; ADP, adenosine diphosphate; ATP, adenosinetriphos ing a glucuronide. phate; UDP, uridine diphosphate; UTP, uridine triphosphate; Thus glycogen accumulation requires systems UDPG, uridine diphosphate glucose; UDPGA, uridine diphos phate glucuronic acid; G-1-P, glucose-i-phosphate; G-6-P, for the regeneration of UTP and G-1-P, and their glucose-6-phosphate; DPN, diphosphopyridine nucleotide; subsequent conversion to UDPG by UDPG pyro TPN, triphosphopyridine nucleotide; GDP, guanosine diphos phosphorylase, and the presence of glycogen syn phate; CDP, cytidine diphosphate; IDP, inosine diphosphate. thetase to accomplish the transfer of glucose resi Received for publication May 22, 1961. dues of UDPG to an existent glucose polymer. 131

However, the presence of a synthesis system in BIocHEMIC@u@ PROCEDURES the tissue does not in itself provide for glycogen Glycogen synthetase was assayed according to storage, unless the glycogen-removing enzyme, Leloir and Goldemberg (16) in a system contain phosphorylase, is functioning at a normal or sub ing (in pmoles/0.115 ml), glycine buffer, pH 8.6, normal rate. 50; glucose-6-phosphate, pH 7, 0.825 ; UDPG, 0.5; This paper reports the activities of various en glycogen, 1 mg. ; and tissue homogenate, 0.01 ml. zymes responsible for the synthesis and degrada The digests were incubated at 87Â°C. for 10 mm tion of glycogen in tumor extracts, along with con utes and inactivated by boiling at 100Â° C. for 30 trol experiments on liver and muscle of both nor seconds, and the liberated UDP was estimated. mal and tumor-bearing animals. UDPG pyrophosphorylase digests consisted of MATERIALS AND METHODS (in @moles/3 ml), Tris-maleate buffer, pH 7.6, 100; UDPG, 1.25; magnesium chloride, 100; cysteine, CHEMICALS 1.59; TPN, 0.20; G-6-P dehydrogenase, 0.1 K The nucleotides (AMP, ADP, ATP, [JDP, units; phosphoglucomutase, 0.4 units; sodium py UDPG, DPN, TPN), sugar phosphates (G-1-P, rophosphate, 1.0; and 0.02 ml. of the supernatant G-6-P), G-6-P dehydrogenase Type IV, and pyru from a 10 per cent tissue homogenate. The control vate kinase were obtained from Sigma Chemical digest did not contain pyrophosphate. Equilibrium Co. Phosphopyruvate (tricyclohexyl amine salt) values were usually attained within 15â€”30minutes and myokinase were products of Mann Research of incubation at 37Â°C. The tumors, however, Laboratories, and rabbit liver glycogen of Nutri showed a lag period. The rise in extinction at 340 tional Biochemicals Corp. All other chemicals were m@ in the presence of TPN, phosphoglucomutase, the best reagent grade available from commercial and glucose-6-phosphate dehydrogenase was used sources. Crystalline phosphoglucomutase and as a measure of G-1-P concentration formed from adenylic acid deaminase were prepared according UDPG and pyrophosphate upon addition of the to Naj jar (24) and Kaickar (13), respectively. enzyme (22, 37). TRANSPLANTABLE MOUSE AND RAT TuMoRs Pi,ruvate kinase was measured by the system The studies reported here were carried out with employed for UDP or ADP estimation. The di the following tumors: Sarcoma 37 in white Swiss gests contained (in @imoles/0.5 ml) triethano mice, lymphatic leukemia in AKR mice, melanoma lamine buffer, pH 7.6, 30; phosphopyruvate, 0.9; in DBA/1J mice, Novikoff hepatoma in Sprague magnesium sulfate, 5 ; UDP or ADP, 0.1 ; and en Dawley rats, and Walker 256 carcinosarcoma in zyme supernatant, 0.05 ml. The pyruvate liberat Wistar rats. Normal mice and rats of the same ed was measured as a color complex with 2,4,- strain were used as control animals. dinitrophenyl hydrazine (16), after incubation at 370 C. for 15 mm. PREPARATION OF HOMOGENATES Nucleoside diphosphokinase was assayed ac AND SUPERNATANTS cording to the procedure of Berg and Joklik (4) The rats were stunned, decapitated, and bled, measuring ADP formation with myokinase and and the mice sacrificed by cervical dislocation. The adenylic acid deamiriase (23). livers, muscles, and tumors were quickly excised Phosphoglucomutase and UDPG dehydrogenase and placed in beakers surrounded by cracked ice. were assayed by procedures described by Najjar The tumors were freed as much as possible of ne (25) and Strominger et al. (36), respectively. crotic and connective tissue. Muscle was taken Phosphorylase activity was measured in the from the hind legs. Tissues were minced with scis presence and absence of 5'-AMP. The digests sors, and 10 per cent homogenates were prepared contained (in @imoles/ml), sodium citrate buffer, in ice-cold 0.25 M sucrose containing 0.001 M ver pH 5.9, 20; potassium fluoride, 46; G-1-P, pH 7.3, sene. Homogenization was carried out with a teflon 10; glycogen, 2 mg.; AMP, 0.04; 10 per cent ho pestle turning at about 600 r.p.m. for exactly 3 mogenate, 0.1 ml. The amount of inorganic phos minutes. The supernatant fluid was obtained by phate liberated was estimated according to Fiske centrifuging the tissue homogenates at 100,000 and Subbarow, with the presence or absence of Xg for 35 minutes at 00 C. A refrigerated Spin 5'-AMP used as a measure of the phosphorylase CO Model L centrifuge was used. About 1 gm. of a and b activities in the tissue extracts. tissue was added to hot KOH for glycogen esti Glycogen was isolated from hot KOH as de mation. scribed by Good, Kramer, and Somogyi (9) and, Glycogen synthetase and UDPG pyrophos after acid hydrolysis, estimated as glucose by the phorylase in the homogenate were assayed the Nelson (26) method.. same day. The remaining enzyme solutions were For the determination of glucose and oligo divided in tubes and frozen at â€”20Â°C. saccharides the tissue was extracted with 70 per

Downloaded from cancerres.aacrjournals.org on September 25, 2021. © 1962 American Association for Cancer Research. NIGAM et al.â€”Limiting Enzymes and Glycogen Storage 133 cent ethanol for 24 hr. at 0Â°â€”5Â°C.,centrifuged, of glucosyl oligosaceharides in the liver has been concentrated, and chromatographed. The individ shown by Fishman and Sie (7) and their origin ual sugars were eluted from the paper and esti traced by Olavarria (29) as owing to the presence mated as glucose, as described by Nigam and of enzymes in liver which make labeled maltose, Gin (27). maltotriose, maltotetraose, and other homologs RESULTS from glycogen-C'4. A rapid decrease in the con Glycogen content of tumors and of the liver and centration of the oligosaccharides during fasting muscle of normal and tumor-bearing animak.â€”The has also been reported (32). A situation similar to low content of glycogen in tumors has been re fasting occurred during the growth of the liver ported by LePage (18) and others (2, 10). In the tumor. Six days after the implantation of the case of hepatoma, it has been shown that tumor tumor the animal lost its store of glycogen, with formation brings a subsequent decrease in the a subsequent decrease in the oligosaccharides. The glycogen content of the liver of host animals (10). tumor itself showed complete absence of maltose, In Table 1, these observations are confirmed for maltotriose, or maltotetraose. Table 2 gives the a number of transplanted tumors. The experiment values for the oligosaccharide composition of Novi shows that in the Novikoff hepatoma-bearing rats koff hepatoma and the liver of normal and tumor the liver and muscle lost most of their glycogen 7 bearing animals. The decrease in the oligosac days after the transplantation of the tumor. On charides shows the participation of a-glucosidases the other hand, the glycogen content of the liver in the liver, which bring about the breakdown of and muscle of sarcoma- and leukemia-bearing the saccharides to glucose for its further metabo hosts was unaltered as compared with normal lism. The presence of a maltase in liver (8) and animals. hepatoma (unpublished results) has been ob Oligosaceharide composition of liver and tumor served. during growth of NOVI/COffhepaloma.â€”The presence Behavior of tumor enzymes involved in glycogen

TABLE 1 GLYCOGEN5 CONTENT OF TUMORS AND OF LIvERS AND MuscLEs OF NORMAL AND TUMOR-BEARING ANIMAIst

TUMORNovlkoffhepatomaAsutAi.8 szaawoLivzii MUSCLE

wet tissue)

0.9Â± 0.1(187Â± 68 0.7Â± 0.10(13 Â±5.1 0.9Â±0.1 Walker256sarcoma 256 Â± 89 (226Â±120 28.5Â±17.0 (18 Â±8.0 2.5Â±2.1 Sarcoma 37 183 Â± 58 (131Â± 25 14.0Â± 4.8 (13 Â±5.0 2.0Â±1.4 Leukemia 240 Â±180 (165Â± 82 10.7Â± 4.4 ( 7.2Â±2.6 5.3Â±1.4 Melanoma(j@moIes/gm 197 Â± 25 (208Â±130 10.0Â± 6.0 (7.4Â±2.2 4.4Â±2.0

* Figures in parentheses represent glycogen content of normal liver and muscle of the same strain of ani mals. The values are means of 6â€”9analyses with standard deviation. t Ashexose.

TABLE 2 COMPOSITION OF GLUCOSYL OLIGOSACCHARIDES IN NOvIK0FF HEPATOMA AND IN LIVER OF NORMAL AND HEPATOMA-BEA.RING ANIMALS

arnroaaRati(N0IULAL)Livza (uzpaoae&-s,@azxo)NOVILOFI SuoassLIVES

Rat4Glucose RatSRatS Rat4RatS

gm wet tissue)

117 93 55 59 70 Maltose 81 89 39 47 0 0 Maltotriose 100 100 0 0 0 0 Maltotetraose 95 107 0 0 0 0 Higher saccbarides*(mg/100 140 180 32 2858 24 26

* Includes maltopentaose, hexaose, and other saccharides immovable on paper chro matogram in acetone: butanol: water (7:2:1) solvent, but free of glycogen.

synthesis.â€”Hexokinase: The presence of hexo were assayed in the five tumors to ascertain kinase has been demonstrated in tumors (5, 20). whether normal phosphorylation of UDP is ac The work of Boyland, of Meyerhof, and of LePage complished in the tumors. The results showed that on tumor glycolysis has established the participa the levels of pyruvate kinase in tumors (4.0-8.0 tion of hexokinase and enzymes of the Embden j@moles pyruvate formed per gm. wet tissue per Meyerhof pathway. Since enzyme systems re hour for ADP, 2.2â€”3.0 for UDP) were close to the generating ATP were present in tumors, as shown level observed in liver (3.5â€”6.1 for ADP and 1.7â€” later in the paper, it is probable that the initial 2.0 for UDP) and muscle (4.4â€”6.8for ADP and step of glucose phosphorylation is accomplished. 2.3â€”2.8for UDP) tissues. There was no significant Phosphoglucomutase: The transformation of difference between the levels in the livers and glucose to G-6-P offers at least three pathways for muscles of normal and tumor-bearing animals. the phosphorylated ester. The glycolytic reaction The nucleoside diphosphokinase activity also resulting in the formation of the lactate, aldol, or showed similarity between the tumor and the com ketol type of rearrangement of hexose phosphates parable liver and muscle tissues. Since pyruvate to heptulose phosphate (33) or the interconversion kinase shows preference for ADP over UDP and of G-6-P to G-1-P. The operation of lactate forma tumor tissues contain larger concentration of ade tion (1) and heptulose production (28) as observed nine nucleotides than uridine nucleotides (31), it in tumors could offer competition for the third is possible that pyruvate kinase would accomplish TABLE 3 PHOSPHOGLUCOMUTASE AcTlvrrY OF TUMORS AND OF LIVER AND MUSCLE OF TUMOR-BEARING ANIMALS

TUMORNovikoffANIMALS BEABUiGLivanMuscLE

G-l-P wet tissue/hour*)

hepatoma 788 Â±201 (713Â± 29 1547Â±148 (1144Â± 76 25 Walker 256 sarcoma 787Â±141 (813Â±115 1409Â±210(1422Â±210 288Â±170 Sarcoma37 806Â± 94(1013Â± 61 1840Â± 50(1151Â±152 184Â±115 Leukemia 765Â±126 (945, 710) 1045Â±153(1158,1241) 96Â± 80 Melanoma(jimoles 934 Â± 48 (568, 874)transformed/gm1229 Â±190 (1320, 1180)65Â± 882 Â± 74

* Figures in parentheses represent enzyme activities for normal liver and muscle of the same strain of animals. Values are the mean of three or more analyses with standard deviation. Where only two analyses were carried out both values are given.

(phosphoglucomutase) reaction. The possibility ATP regeneration and nucleoside diphosphokinase of substrate channeling for the first two reactions the phosphorylation of UDP at the expense of is more probable because of low phosphoglu ATP. Mills et al. (21) have come to a similar con comutase activity observed in most tumors. clusion for the biosynthesis of UTP. Table 3 provides data on the phosphoglucomutase UDPG synthesis (assay of UDPG pyrophos level in the five tumors with comparable values for phorylase activity).â€”UDPG synthesis is accom liver and muscle. These data support the findings plished in most animal tissues through transphos of Weber and Cantero (39) for Novikoff hepatoma, phorylation involving G-1-P and UTP mediated and of Weber et a!. (38) for the Morris hepatoma, by UDPG pyrophosphorylase (14). The activities who observed low activities for phosphoglucomu of UDPG pyrophosphorylase for various tumor tase in the two tumors. tissues and of liver and muscle of normal and tu Enzymes involved in UTP regeneration.â€”The mor-bearing animals are presented in Table 4. It phosphorylation of UDP to UTP can be brought can be observed that UDPG pyrophosphorylase about by two enzymes, pyruvate kinase and nu levels in all tumors except melanoma were lower cleoside diphosphokinase. Pyruvate kinase utilizes than those in liver or muscle. The decreases varied phosphoenolpyruvate formed during glucose ca between 50 and 65 per cent of liver values, the tabolism for the phosphorylation of ADP, CDP, lower range representing leukemia and the higher GDP, and UDP (34), leaving behind pyruvate for ones Novikoff hepatoma, Sarcoma 37, and Walker lactate production. On the other hand, nucleoside 256 carcinosarcoma. Melanoma showed distinct diphosphokinase uses the regenerated ATP for difference in having an activity close to that of UDP or IDP phosphorylation (4). Both enzymes liver. The fact that this enzyme is present in

Downloaded from cancerres.aacrjournals.org on September 25, 2021. © 1962 American Association for Cancer Research. NIGAM et al.â€”Limiling Enzymes and Glycogen Storage 13@ tumor tissues would suggest that the formation One requires the use of phosphorylase in the ac of UDPG will take place if G-1-P and UTP are tivated form and the other amylolytic enzymes. the available substrates. The statement is support Earlier studies have demonstrated ractivation of ed by the observed presence of UDPG in tumors muscle and tumor phosphoryla.se by AMP (6, 11). (31). The amylolytic activity against glycogen is con Enzyme utilizing UDPG (UDPG dehydrogenase). siderably lower in liver (32) and absent in muscle. â€”A DPN-dependent dehydrogenase has been de It has been suggested that the major function of scribed by Strominger et al. (35) capable of con the phosphorylase is the degradation of glycogen verting UDP-glucose to UDP-glucuronic acid. (3). The present studies have been carried out with UDPGA is known to be further metabolized in a the idea that only phosphorylase contributes to transglycosylase reaction resulting in formation of glycogen degradation and amylase plays but a glucuronides of organic substances. Thus, diver minor role. The phosphorylase activity of tumor sion of UDPG from glycogen synthesis toward glu-. and of liver and muscle was estimated both in the curonide formation is a possibility. However, assay presence and absence of AMP. It was observed of UDPG dehydrogenase activity in tumors, that phosphorylase of tumor is more active than muscle, and liver showed its complete absence in of liver and is activated to a greater extent by tumor as well as muscle and significant activity in AMP. However, the activation is less than that

TABLE 4 UDPG PYROPHOSPHORYLASE Acmrn'Y OF TUMOR AND LivEn TissuEs

TUMORNovikoffANIMALS BEARINGLivanMUSCLE

G-1-P wet tissue/hour5)

hepatoma 194Â± 6.0(210Â± 5.2) 220Â±14.0 (288Â±11.0) 76Â±7.6 Walker256 sarcoma 188Â± 4.5 (208Â± 4.8) 225Â± 8.0 (245Â±18.4) 68Â±9.0 Sarcoma 37 90Â±14.8(108Â±11.5) 172Â± 7.6 (165Â±11.5) 86Â±8.4 Leukemia 108Â±12.5(101Â±14.0) 180Â±10.0(158Â±15.0) 50Â±5.4 Melanoma(jimoles 115Â±10.0(113Â± 5.8)formed/gm205Â± 8.0 (200Â±11.0) 114Â±7.6

5Figures in parentheses represent activity of normal liver and muscle of the same strain of animals. The values are means of three analyses with standard deviation. Incubation time for the digests was 30 mm. at 37Â°C. for these determinations. the liver. It can, therefore, be concluded that the TABLE 5 store of UDPG is not channeled to the other path GLYCOGEN SYNTHETASE AcTIVITY OF [email protected] way. RAT AND MousE ORGANS Glycogen synthetase.â€”Inanimal tissues the par @molesUDP formed/gm wet tissue/hour5 ticipation of glycogen synthetase is mainly re WI5TAR RAT Spa.&aus-Dawi.sy RAT sponsible for glycogen synthesis from UDPG. The Blood hemolysate 22Â±2.0 Liver 208Â±8.0 importance of this enzyme as a controlling factor Brain 72 Â±1.0 Muscle 220Â±4.0 Heart 220Â±3.8 in the accumulation of glycogen in normal animal Diaphragm 181Â±2.0 Swiss MOUSE organs is illustrated in Table 5. It can be seen that Kidney 28Â±0.5 Liver 212 Â±8.8 Liver(embryonic) 300Â±4.0 Muscle 188Â±2.7 glycogen-storing organs like liver, muscle, heart, Liver(1day old) 287 Â±4.0 and diaphragm showed a higher level of enzyme Liver(adult) 222Â±3.9 DBAMOUSS activity than did organs such as spleen, lung, kid Lung 55 Â±1.0 Liver 286Â±4.2 Muscle 240Â±4.2 Muscle 288Â±4.1 ney, and blood, which store little glycogen. For Intestine (small) 88Â±.05 tumor tissues a comparable representation of gly Spleen 48 Â±1.0 AKR MOUSS cogen synthetase activity is given in Table 6. The Liver 200Â±4.0 Muscle 195 Â±8.9 level in tumors is only 20â€”SOpercent of the values 5Values are the means of three analyses with standard de observed in the liver. The activity is close to those viation. found in nonglycogen-storing organs like lung, spleen, etc. It is noteworthy that leg muscles of observed for muscle. It is noteworthy that AMP leukemia-, melanoma-, and sarcomas-bearing ani activated phosphorylase activity of liver is con mals showed a much lower level of enzyme ac siderably lower than that in muscle and at the tivity. same time liver accumulates nearly 10 times more L)egradative removal of glycogen in tumors .â€”Gly glycogen than muscle. The muscle thus shows cogen can be degraded via two major pathways. strong capacity for glycogen synthesis and an

equally active degradation of the polymer. On the prior to the elucidation of the new pathway. The other hand, some tumor tissues, though defective accumulated data were based mostly on the assay in glycogen synthetase, are capable of degrading of phosphorylase activity in various tumor tissues, glycogen better than is liver. and no definite reasons could be offered to explain the low glycogen level in the presence of normal DISCUSSION phosphorylase activity. Recent work of Leloir and co-workers (15, 17) In the studies reported here enzymes of Chart 1 and of Robbins and Lipmann (30) has clearly responsible for the conversion of glucose to glyco demonstrated that the main function of phos- gen have been assayed for tumor and comparable phorylase is the degradation of glycogen rather normal tissues. It is observed that the presence of than its synthesis. A new pathway has been dem- the hexokinase- and ATP-regenerating system ac onstrated by these workers which involves the me- complishes glucose phosphorylation. However, a diation of UDP-glucose. A representation of the metabolic block is encountered in the conversion series of reactions which convert glucose to glyco- of G-6-P to G-1-P because of low activity of phos gen in normal and tumor tissues is shown in phoglucomutase. This necessarily would provide Chart 1. reduced G-1-P level in the presence of competing The work on glycogen synthesis was carried out systems of glycolysis and heptulose formation. TABLE 6 GLYCOGEN SYNTHETASE ACTiVITY OF TuMoRs AND MUScLES ANDLIVERs OF TUMOR-BEARINGANIMALS

LiverMuscleTumorT/LX100Novikoffhepatoma

UDP formed/gin wet tissue/hour5)

245Â±8.8 166Â±3.0 48Â±0.9 20 Walker256sarcoma 275Â±4.2 48Â±1.0 54Â±1.0 20 Sarcoma37 226Â±8.0 46Â±1.1 48Â±1.0 21 Leukemia 205Â±2.8 70Â±1.5 65Â±0.5 32 Melanoma(,@mo1es 200Â±8.1 58Â±1.4 66Â±0.7 33

S Values are the means of three analyses with standard deviation.

The G-1-P would, however, be in equilibrium with @ GLUCOSE @,G-&P with the quantity formed by the cleavage of gly ATP I.@DP/ cogen carried out by tumor phosphorylase. At this stage it is not possible to explain the significance of higher G-1-P levels reported for certain tumors @ PEP AMP by LePage (18). @ PYRIJVATE GIP +INORG.PHOSPt-JATE The presence of adequate amounts of pyruvate I @UTP kinase and nucleoside diphosphokinase in tumors makes it possible for the UTP to be regenerated. L@CTATE(7 3 \N@\N Pyruvate kinase, as well as phosphoglycerate Id nase, accomplishes the phosphorylation of ADP to UDP+ &UCOSE) ATP. ATP formed can be utilized for a variety of processes including the phosphorylation of hexoses, @ )@PN GL@OSE pentoses, and their monophosphates, and the purine and pyrimidine mono- and diphosphates. The last reaction carried out by nucleoside diphos-. CHART1.â€”Glycogensynthesis and degradation in normal phokinase could accomplish UTP formation animal tissues and tumor tissues. The enzymes in tumors that occur with diminished activity are shown with one or from UDP at the expense of regenerated ATP. more cross bars in order of decreased activity. 1. Hexokinase. Thus, a balance of enzyme of E-M pathway and 2. Phosphoglucomutase. 3. UDPG pyrophosphorylase. 4. Gly glucose can provide energy and a supply of nucleo cogen synthetase. 5. Phosphorylase. 6. Pyruvate kinase. 7. tides all at the expense of glucose catabolism. Embden-Meyerhof pathway. 8. Nucleoside diphosphoidnase. From the preceding discussion it can be seen 9. Diphosphoglycerate-phosphoglycerate kinase system. 10. UDPG dehydrogenase. 11. Amylase PP, pyrophosphate; PEP, that, in case phosphoglucomutase is a limiting en phosphoenolpyruvate. zyme, a reduced supply of G-1-P would be avail

Downloaded from cancerres.aacrjournals.org on September 25, 2021. © 1962 American Association for Cancer Research. NIGAM et al.â€”Limiting Enzymes and Glycogen Storage 137 able for the next synthetic step involved in the 4. BERG, P., and JOKLIK,W. K. Enzymatic Phosphorylation formation of UDPG by UDPG pyrophosphory of Nucleoside Diphosphates. J. Biol. Chem., 210:657â€”71, 1954. lase. UDPG pyrophosphorylase is present in all 5. Bom@su, E. ; Goim, G. C. L. ; and WILLIAMS-ABIIMAN, tumors. The activity varies from SO to 50 per cent H. G. Hexokinase Activity of Animal Tumors. Biochem. J., of liver values, with the exception of melanoma. 49:321â€”25,1951. In case of melanoma the enzyme level is the same 6. Coiu, G. T. ; ILLINGWORTH, B. ; and KELLER, P. J. En as in liver. Because of the variations in activity of zymes of Carbohydrate Metabolism. In: Methods in En zymology, 1:200â€”205. 1st ed. New York: Academic Press, UDPG pyrophosphorylase, it cannot be chiefly 1955. responsible for limiting glycogen accumulation in 7. FISHMAN, W. H., and SIE, H. G. Presence of Maltose, Mal all tumors. At best a lower level of enzyme would totriose, and Maltotetraose in Liver. J. Am. Chem. Soc., reduce the rate of UDPG synthesis for certain 80:121-28, 1958. 8. Gmi, K. V.; NAGABHUSHANAM,A.;Nm&s, V. N. ; and tumors. BEi..&v@trn, B. Enzymatic Synthesis of Oligosaccharides The observed absence of UDPG dehydrogenase from Maltose by Rat Liver. Science, 121:898, 1955. in tumors would effectively block any transforma 9. GooD, C. A.; KRAMER, H.; and SOMOGYT,M. Determina tion of UDPG to UDPGA, and the UDPG formed tion of Glycogen. J. Biol. Chem., 100:485â€”91, 1938. 10. GORANSON,E.S. Enzymes. In: Canadian Cancer Confer will be utilized mainly for the formation of glyco ence, 1:330â€”42. 1st ed. New York: Academic Press, 1955. gen, by glycogen synthetase. However, the later 11. GORANSON,E. S.; McBiunE, J.; and WEBER, G. Phos enzyme is deficient in tumors. Its activity varies phorylase Activity in Rat Hepatoma and Mouse Mam between 20 and 30 per cent of liver values for all mary Carcinoma Transplants. Cancer Research, 14:227- tumors, a level similar to that observed in all non 31, 1954. 12. GREENSTEIN, J. P. Chemistry of Tumors. in: Biochemis glycogen-storing normal animal organs. Thus, this try of Cancer, pp. 447-60. 2d ed. New York: Academic enzyme would seem to be mainly responsible for Press, 1954. lowered glycogen synthesis in tumor tissues. 13. KAu@Aa, H. M. Differential Spectrophotometry of Purine Studies on glycogen depletion during starvation Compounds by Means of Specific Enzymes. Ill. Studies also reveal changes in the intracellular distribution of the Enzymes of Purine Metabolism. J. Biol. Chem., 167:429â€”61,1947. of glycogen synthetase (19). 14. [email protected],H.M., and Cuvow, E. lie Congr. 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Vijai N. Nigam, Helen L. MacDonald and A. Cantero

Cancer Res 1962;22:131-138.

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