DOCSLIB.ORG

Biochemistry Entry of Fructose and Galactose

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Biochemistry Entry of Fructose and Galactose Paper : 04 Metabolism of carbohydrates Module : 06 Entry of Fructose and Galactose Dr. Vijaya Khader Dr. MC Varadaraj Principal Investigator Dr.S.K.Khare,Professor IIT Delhi. Paper Coordinator Dr. Ramesh Kothari,Professor UGC-CAS Department of Biosciences Saurashtra University, Rajkot-5, Gujarat-INDIA Dr. S. P. Singh, Professor Content Reviewer UGC-CAS Department of Biosciences Saurashtra University, Rajkot-5, Gujarat-INDIA Dr. Charmy Kothari, Assistant Professor Content Writer Department of Biotechnology Christ College, Affiliated to Saurashtra University, Rajkot-5, Gujarat-INDIA 1 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose Description of Module Subject Name Biochemistry Paper Name 04 Metabolism of Carbohydrates Module Name/Title 06 Entry of Fructose and Galactose 2 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose METABOLISM OF FRUCTOSE Objectives 1. To study the major pathway of fructose metabolism 2. To study specialized pathways of fructose metabolism 3. To study metabolism of galactose 4. To study disorders of galactose metabolism 3 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose Introduction Sucrose disaccharide contains glucose and fructose as monomers. Sucrose can be utilized as a major source of energy. Sucrose includes sugar beets, sugar cane, sorghum, maple sugar pineapple, ripe fruits and honey Corn syrup is recognized as high fructose corn syrup which gives the impression that it is very rich in fructose content but the difference between the fructose content in sucrose and high fructose corn syrup is only 5-10%. HFCS is rich in fructose because the sucrose extracted from the corn syrup is treated with the enzyme that converts some glucose in fructose which makes it more sweet. Fructose is a product of sucrose hydrolysis and is probably the second most abundant dietary sugar after glucose The major pathway of fructose metabolism 1. Fructose is phosphorylated by ATP through the action of two different kinases. Yeast glucokinase forms fructose-6-phosphate. In liver and muscle fructose is phosphorylated by a specific fructokinase yielding fructose-1-phosphoate 4 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose a. Fructokinase is found in the liver, kidney and small intestine b. The enzyme has a very low Michalis constant (i.e., a high affinity) for fructose c. The activity is not affected by feeding-fasting cycles or by insulin 2. Phosphofructoaldolase (aldolase B) catalyzes the cleavage of D-fructose-1-phosphate a. Phosphofructoaldolase is an isoenzyme of the glycolytic pathway aldolase b. It is abundant in the liver 3. The fate of D-glyceraldehyde may take several routes a. Phosphorylation to D-glyceraldehyde-3-phosphate and metabolism by the glycolytic pathway or the gluconeogenic pathway b. Oxidation to D-glycerate by an NAD+ linked glyceraldehyde dehydrogenase . D- glycerate may then be converted to L-serine via hydroxypyruvate c. Reduction to glycerol by an NADH+ linked glycerol dehydrogenase, followed by phosphorylation to glycerol-3-phosphate. The latter may be used for gluconeogenesis or triglyceride synthesis 5 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose Specialized pathways of fructose metabolism 1. Fructose metabolism in spermatozoa a. Fructose is the major energy source for spermatozoa and is formed from glucose in the seminal vesicle b. The pathway involves reduction of glucose to D-sorbitol and oxidation of the latter to D-fructose c. The fructose concentration of semen may reach to 10 mM. Most of this is available for the spermatozoal because fructose is utilized sparingly by the other tissues that come in contact with the seminal fluid d. The mitochondria of sperm are the only such organelles to contain lactate dehydrogenase. Because this enzyme is present is present the lactate that is formed by fructolysis can be completely oxidized to CO2 and H2O without the need for a shuttle system to transport reducing equivalents into the mitochondria 2. Sorbitol metabolism in diabetes a. The formation of sorbitol from glucose proceeds rapidly in the lens of the eye and in the Schwann cells of the nervous system b. Sorbitol cannot pass through the cell membrane and in the diabetic, sorbitol levels build up in these cells because the rate of oxidation of sorbitol to fructose is decreased 6 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose c. It is thought that the elevated sorbitol concentration causes an increase in osmotic pressure which might be a causative factor in the development of the lens cataracts and the neural dysfunction that occur in diabetes. Defects in fructose metabolism 1. Essential fructosuria In this case fructose is not converted into fructose-1-phosphate due to the deficiency of enzyme hepatic fructokinase . Restriction of dietary fructose is the remedy 2. Hereditary fructose intolerance Hereditary fructose intolerance is a genetic disorder characterized by vomiting and hypoglycemia after ingestion of fructose or fructose producing foods (e.g., sucrose, sorbitol) a. It is an autosomal recessive condition involving a deficiency of fructose-1-phosphate aldolase b. Eating a meal containing fructose causes an accumulation of fructose -1-phosphate in tissues, which is believed to underlie the hepatic and renal damage found in the condition c. Several enzymatic activities are inhibited by high cellular levels of fructose-1- phosphate Fructokinase: its deficiency leads to frutosemia and fructosuria Hepatic glycogen phosphorylase: the lack is in part responsible for the postprandial hypoglycemia and glucagon unresponsiveness Fructose 1,6-diphosphate aldolase: without it gluconeogenesis is blocked, contributing to the postprandial hypoglycemia 3. Consumption of high fructose Fructokinase rapidly converts fructose to frutcose-1-phosphate. The activity of the enzyme aldolase B is relatively less and due to this fructose-1-phosphate accumulates in the cell. This leads to the depletion of intracellular inorganic phosphate levels. The phenomenon of binding of Pi to the organic molecules leads to the less availability of Pi for essential metabolic function and is known as 7 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose sequestering of phosphate. Due to the decreased availability of Pi, which happens in overconsumption of fructose the liver metabolism is adversely affected. This includes the lower synthesis of Tap from ADP and Pi. High consumption of fructose over a long period is associated with increase uric acid blood leading to gout. This due to the excessive breakdown of ADP and AMP to uric acid Metabolism of Galactose 1. Lactose is hydrolyzed to yield galactose and glucose in the small intestine of infants and small children by one form of enzyme, which enters the blood stream from the intestine. An adult form of the enzyme is less active and is missing in many adults, leading to a low tolerance for milk and for milk products containing lactose 2. Galactose is phosphorylated by galactokinase to form galactose-1-phosphate 3. Hexose -1-phosphate uridyl transferase catalyzes the transfer of UDP from UDP- glucose to galactose-1-phosphate, to form UDP-galactose and glucose-1-phosphate 4. An epimerase converts UDP-galactose to UDP-glucose 8 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose Disorders of galactose metabolism A. Classical galactosemia- This is due to the deficiency of the enzyme galactose-1- phophosphate uridyltranferase. 1. It is a rare congenital disease in infants 2. Autosomal recessive disorder 3. An excessive accumulation of galactose is due to inborn errors of galactose metabolism 4. Aldol reductase converts excess galactose into galactitol. Galactitol is associated in the development of cataract 5. Accumulation of galactose 1-phosphate in liver results in the depletion of inorganic phosphate for other metabolic functions 6. Symptoms include loss of weight in infants, jaundice, mental retardation etc. In severe case amino aciduria, albuminuria are also observed 7. Diet deprived of galactose and lactose is the remedy B. Galactokinase deficiency- In this condition there is an accumulation of galactose in blood and tissues. In this defective enzyme galactokinase responsible for the phosphorylation of galactose will also result in galactosemia and galactosuria. Here again galactose is shunted to the formation of galactitol. Generally galactokinase deficient individuals do not develop hepatic and renal complications C. Uridine diphosphate galactose-4-epimerase deficiency- It is autosomal recessive disorder. This deficiency prevents the conversion of modified form (UDP-galactose) to another modified form (UDP- glucose). As a result compound associated with galactose processing gets accumulated to toxic levels. Symptoms include cataract, intellectual disability and kidney brain and liver are damaged. 9 Metabolism of Carbohydrates Biochemistry Entry of Fructose and Galactose .
Load more

Recommended publications
  • Molecular Characterization of Galactokinase Deficiency In
    J Hum Genet (1999) 44:377–382 © Jpn Soc Hum Genet and Springer-Verlag 1999377 ORIGINAL ARTICLE Minoru Asada · Yoshiyuki Okano · Takuji Imamura Itsujin Suyama · Yutaka Hase · Gen Isshiki Molecular characterization of galactokinase deficiency in Japanese patients Received: May 19, 1999 / Accepted: August 21, 1999 Abstract Galactokinase (GALK) deficiency is an autoso- Key words Galactosemia · Galactokinase (GALK) · Muta- mal recessive disorder, which causes cataract formation in tion · Genotype · Phenotype children not maintained on a lactose-free diet. We charac- terized the human GALK gene by screening a Japanese genomic DNA phage library, and found that several nucle- otides in the 59-untranslated region and introns 1, 2, and 5 in Introduction our GALK genomic analysis differed from published data. A 20-bp tandem repeat was found in three places in intron Galactokinase (GALK: McKUSICK 230200) is the first 5, which were considered insertion sequences. We identified enzyme in the Leloir pathway of galactose metabolism; it five novel mutations in seven unrelated Japanese patients catalyzes the phosphorylation of galactose to galactose- with GALK deficiency. There were three missense muta- 1-phosphate. GALK deficiency, first described in 1965 tions and two deletions. All three missense mutations (Gitzelmann 1965), is an autosomal recessive genetic disor- (R256W, T344M, and G349S) occurred at CpG dinucle- der with an incidence of 1/1,000,000 in Japan (Aoki and otides, and the T344M and G349S mutations occurred in Wada 1988) on newborn mass screening and an incidence of the conserved region. The three missense mutations led to a 1/1,000,000 in Caucasians (Segal and Berry 1995).
    [Show full text]
  • Gene Symbol Gene Description ACVR1B Activin a Receptor, Type IB
    Table S1. Kinase clones included in human kinase cDNA library for yeast two-hybrid screening Gene Symbol Gene Description ACVR1B activin A receptor, type IB ADCK2 aarF domain containing kinase 2 ADCK4 aarF domain containing kinase 4 AGK multiple substrate lipid kinase;MULK AK1 adenylate kinase 1 AK3 adenylate kinase 3 like 1 AK3L1 adenylate kinase 3 ALDH18A1 aldehyde dehydrogenase 18 family, member A1;ALDH18A1 ALK anaplastic lymphoma kinase (Ki-1) ALPK1 alpha-kinase 1 ALPK2 alpha-kinase 2 AMHR2 anti-Mullerian hormone receptor, type II ARAF v-raf murine sarcoma 3611 viral oncogene homolog 1 ARSG arylsulfatase G;ARSG AURKB aurora kinase B AURKC aurora kinase C BCKDK branched chain alpha-ketoacid dehydrogenase kinase BMPR1A bone morphogenetic protein receptor, type IA BMPR2 bone morphogenetic protein receptor, type II (serine/threonine kinase) BRAF v-raf murine sarcoma viral oncogene homolog B1 BRD3 bromodomain containing 3 BRD4 bromodomain containing 4 BTK Bruton agammaglobulinemia tyrosine kinase BUB1 BUB1 budding uninhibited by benzimidazoles 1 homolog (yeast) BUB1B BUB1 budding uninhibited by benzimidazoles 1 homolog beta (yeast) C9orf98 chromosome 9 open reading frame 98;C9orf98 CABC1 chaperone, ABC1 activity of bc1 complex like (S. pombe) CALM1 calmodulin 1 (phosphorylase kinase, delta) CALM2 calmodulin 2 (phosphorylase kinase, delta) CALM3 calmodulin 3 (phosphorylase kinase, delta) CAMK1 calcium/calmodulin-dependent protein kinase I CAMK2A calcium/calmodulin-dependent protein kinase (CaM kinase) II alpha CAMK2B calcium/calmodulin-dependent
    [Show full text]
  • • Glycolysis • Gluconeogenesis • Glycogen Synthesis
    Carbohydrate Metabolism! Wichit Suthammarak – Department of Biochemistry, Faculty of Medicine Siriraj Hospital – Aug 1st and 4th, 2014! • Glycolysis • Gluconeogenesis • Glycogen synthesis • Glycogenolysis • Pentose phosphate pathway • Metabolism of other hexoses Carbohydrate Digestion! Digestive enzymes! Polysaccharides/complex carbohydrates Salivary glands Amylase Pancreas Oligosaccharides/dextrins Dextrinase Membrane-bound Microvilli Brush border Maltose Sucrose Lactose Maltase Sucrase Lactase ‘Disaccharidase’ 2 glucose 1 glucose 1 glucose 1 fructose 1 galactose Lactose Intolerance! Cause & Pathophysiology! Normal lactose digestion Lactose intolerance Lactose Lactose Lactose Glucose Small Intestine Lactase lactase X Galactose Bacteria 1 glucose Large Fermentation 1 galactose Intestine gases, organic acid, Normal stools osmotically Lactase deficiency! active molecules • Primary lactase deficiency: อาการ! genetic defect, การสราง lactase ลด ลงเมออายมากขน, พบมากทสด! ปวดทอง, ถายเหลว, คลนไสอาเจยนภาย • Secondary lactase deficiency: หลงจากรบประทานอาหารทม lactose acquired/transient เชน small bowel เปนปรมาณมาก เชนนม! injury, gastroenteritis, inflammatory bowel disease! Absorption of Hexoses! Site: duodenum! Intestinal lumen Enterocytes Membrane Transporter! Blood SGLT1: sodium-glucose transporter Na+" Na+" •! Presents at the apical membrane ! of enterocytes! SGLT1 Glucose" Glucose" •! Co-transports Na+ and glucose/! Galactose" Galactose" galactose! GLUT2 Fructose" Fructose" GLUT5 GLUT5 •! Transports fructose from the ! intestinal lumen into enterocytes!
    [Show full text]
  • Pentose PO4 Pathway, Fructose, Galactose Metabolism.Pptx
    Pentose PO4 pathway, Fructose, galactose metabolism The Entner Doudoroff pathway begins with hexokinase producing Glucose 6 PO4 , but produce only one ATP. This pathway prevalent in anaerobes such as Pseudomonas, they doe not have a Phosphofructokinase. The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) is a biochemical pathway parallel to glycolysis that generates NADPH and pentoses. While it does involve oxidation of glucose, its primary role is anabolic rather than catabolic. There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars. For most organisms, the pentose phosphate pathway takes place in the cytosol. For each mole of glucose 6 PO4 metabolized to ribulose 5 PO4, 2 moles of NADPH are produced. 6-Phosphogluconate dh is not only an oxidation step but it’s also a decarboxylation reaction. The primary results of the pathway are: The generation of reducing equivalents, in the form of NADPH, used in reductive biosynthesis reactions within cells (e.g. fatty acid synthesis). Production of ribose-5-phosphate (R5P), used in the synthesis of nucleotides and nucleic acids. Production of erythrose-4-phosphate (E4P), used in the synthesis of aromatic amino acids. Transketolase and transaldolase reactions are similar in that they transfer between carbon chains, transketolases 2 carbon units or transaldolases 3 carbon units. Regulation; Glucose-6-phosphate dehydrogenase is the rate- controlling enzyme of this pathway. It is allosterically stimulated by NADP+. The ratio of NADPH:NADP+ is normally about 100:1 in liver cytosol.
    [Show full text]
  • Enzymatic Encoding Methods for Efficient Synthesis Of
    (19) TZZ__T (11) EP 1 957 644 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C12N 15/10 (2006.01) C12Q 1/68 (2006.01) 01.12.2010 Bulletin 2010/48 C40B 40/06 (2006.01) C40B 50/06 (2006.01) (21) Application number: 06818144.5 (86) International application number: PCT/DK2006/000685 (22) Date of filing: 01.12.2006 (87) International publication number: WO 2007/062664 (07.06.2007 Gazette 2007/23) (54) ENZYMATIC ENCODING METHODS FOR EFFICIENT SYNTHESIS OF LARGE LIBRARIES ENZYMVERMITTELNDE KODIERUNGSMETHODEN FÜR EINE EFFIZIENTE SYNTHESE VON GROSSEN BIBLIOTHEKEN PROCEDES DE CODAGE ENZYMATIQUE DESTINES A LA SYNTHESE EFFICACE DE BIBLIOTHEQUES IMPORTANTES (84) Designated Contracting States: • GOLDBECH, Anne AT BE BG CH CY CZ DE DK EE ES FI FR GB GR DK-2200 Copenhagen N (DK) HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI • DE LEON, Daen SK TR DK-2300 Copenhagen S (DK) Designated Extension States: • KALDOR, Ditte Kievsmose AL BA HR MK RS DK-2880 Bagsvaerd (DK) • SLØK, Frank Abilgaard (30) Priority: 01.12.2005 DK 200501704 DK-3450 Allerød (DK) 02.12.2005 US 741490 P • HUSEMOEN, Birgitte Nystrup DK-2500 Valby (DK) (43) Date of publication of application: • DOLBERG, Johannes 20.08.2008 Bulletin 2008/34 DK-1674 Copenhagen V (DK) • JENSEN, Kim Birkebæk (73) Proprietor: Nuevolution A/S DK-2610 Rødovre (DK) 2100 Copenhagen 0 (DK) • PETERSEN, Lene DK-2100 Copenhagen Ø (DK) (72) Inventors: • NØRREGAARD-MADSEN, Mads • FRANCH, Thomas DK-3460 Birkerød (DK) DK-3070 Snekkersten (DK) • GODSKESEN,
    [Show full text]
  • Hereditary Galactokinase Deficiency J
    Arch Dis Child: first published as 10.1136/adc.46.248.465 on 1 August 1971. Downloaded from Alrchives of Disease in Childhood, 1971, 46, 465. Hereditary Galactokinase Deficiency J. G. H. COOK, N. A. DON, and TREVOR P. MANN From the Royal Alexandra Hospital for Sick Children, Brighton, Sussex Cook, J. G. H., Don, N. A., and Mann, T. P. (1971). Archives of Disease in Childhood, 46, 465. Hereditary galactokinase deficiency. A baby with galactokinase deficiency, a recessive inborn error of galactose metabolism, is des- cribed. The case is exceptional in that there was no evidence of gypsy blood in the family concerned. The investigation of neonatal hyperbilirubinaemia led to the discovery of galactosuria. As noted by others, the paucity of presenting features makes early diagnosis difficult, and detection by biochemical screening seems desirable. Cataract formation, of early onset, appears to be the only severe persisting complication and may be due to the biosynthesis and accumulation of galactitol in the lens. Ophthalmic surgeons need to be aware of this enzyme defect, because with early diagnosis and dietary treatment these lens changes should be reversible. Galactokinase catalyses the conversion of galac- and galactose diabetes had been made in this tose to galactose-l-phosphate, the first of three patient (Fanconi, 1933). In adulthood he was steps in the pathway by which galactose is converted found to have glycosuria as well as galactosuria, and copyright. to glucose (Fig.). an unexpectedly high level of urinary galactitol was detected. He was of average intelligence, and his handicaps, apart from poor vision, appeared to be (1) Galactose Gackinase Galactose-I-phosphate due to neurofibromatosis.
    [Show full text]
  • Induction of Uridyl Transferase Mrna-And Dependency on GAL4 Gene Function (In Vitro Translation/Immunoprecipitation/GAL Gene Cluster/Positive Regulation) JAMES E
    Proc. Nati. Acad. Sci. USA Vol. 75, No. 6, pp. 2878-2882, June 1978 Genetics Regulation of the galactose pathway in Saccharomyces cerevisiae: Induction of uridyl transferase mRNA-and dependency on GAL4 gene function (in vitro translation/immunoprecipitation/GAL gene cluster/positive regulation) JAMES E. HOPPER*, JAMES R. BROACHt, AND LUCY B. ROWE* * Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02154; and t Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724 Communicated by Norman H. Giles, April 10,1978 ABSTRACT In Saccharomyces cerevisiae, utilization of Genetic control of the inducible galactose pathway enzymes galactose requires four inducible enzyme activities. Three of involves the four structural genes GALI, GAL10, GAL7, and these activities (galactose-l-phosphate uridyl transferase, EC genes, GAL4, GAL81 (c), GAL80 2.7.7.10; uridine diphosphogalactose 4-epimerase, EC 5.1.3.2; GAL2 and four regulatory and galactokinase, EC 2.7.1.6) are specified by three tightly (i), and GALS.* Mutations in GALl, GAL10, GAL7, and GAL2 linked genes (GAL7, GALlO, and GALI, respectively) on chro- affect the individual appearance of galactokinase, epimerase, mosome II, whereas the fourth, galactose transport, is specified transferase, and galactose transport activities, respectively (6). by a gene (GALS) located on chromosome XIL Although classic Mutations defining the GALl, GAL10, and GAL7 genes have genetic analysis has revealed both positive and negative regu- invariably been recessive, and they map in three tightly linked latory genes that coordinately affect the appearance of ail four complementation groups near the centromere of chromosome enzyme activities, neither the basic events leading to the ap- pearance of enzyme activities nor the roles of the regulatory II (6, 9, 10).
    [Show full text]
  • Supplementary Materials
    Supplementary Materials Figure S1. Differentially abundant spots between the mid-log phase cells grown on xylan or xylose. Red and blue circles denote spots with increased and decreased abundance respectively in the xylan growth condition. The identities of the circled spots are summarized in Table 3. Figure S2. Differentially abundant spots between the stationary phase cells grown on xylan or xylose. Red and blue circles denote spots with increased and decreased abundance respectively in the xylan growth condition. The identities of the circled spots are summarized in Table 4. S2 Table S1. Summary of the non-polysaccharide degrading proteins identified in the B. proteoclasticus cytosol by 2DE/MALDI-TOF. Protein Locus Location Score pI kDa Pep. Cov. Amino Acid Biosynthesis Acetylornithine aminotransferase, ArgD Bpr_I1809 C 1.7 × 10−4 5.1 43.9 11 34% Aspartate/tyrosine/aromatic aminotransferase Bpr_I2631 C 3.0 × 10−14 4.7 43.8 15 46% Aspartate-semialdehyde dehydrogenase, Asd Bpr_I1664 C 7.6 × 10−18 5.5 40.1 17 50% Branched-chain amino acid aminotransferase, IlvE Bpr_I1650 C 2.4 × 10−12 5.2 39.2 13 32% Cysteine synthase, CysK Bpr_I1089 C 1.9 × 10−13 5.0 32.3 18 72% Diaminopimelate dehydrogenase Bpr_I0298 C 9.6 × 10−16 5.6 35.8 16 49% Dihydrodipicolinate reductase, DapB Bpr_I2453 C 2.7 × 10−6 4.9 27.0 9 46% Glu/Leu/Phe/Val dehydrogenase Bpr_I2129 C 1.2 × 10−30 5.4 48.6 31 64% Imidazole glycerol phosphate synthase Bpr_I1240 C 8.0 × 10−3 4.7 22.5 8 44% glutamine amidotransferase subunit Ketol-acid reductoisomerase, IlvC Bpr_I1657 C 3.8 × 10−16
    [Show full text]
  • LACTOSE & D-GALACTOSE (Rapid)
    www.megazyme.com LACTOSE & D-GALACTOSE (Rapid) ASSAY PROCEDURE K-LACGAR 02/21 Incorporating A Procedure For The Analysis Of “Low- Lactose” Or “Lactose-Free” Samples Containing High Levels Of Monosaccharides (Improved Rapid Format) (*115 Assays per Kit) * The number of tests per kit can be doubled if all volumes are halved The reagents provided in this kit are also suitable for use with AOAC method 2006.06 – Lactose in milk. Patented: US 7,785,771 B2 and EP1 828 407 (GB, FR, IE, DE) © Megazyme 2021 INTRODUCTION: Lactose, or milk sugar, is a white crystalline disaccharide. It is formed in the mammary glands of all lactating animals and is present in their milk. Lactose yields D-galactose and D-glucose on hydrolysis by lactase (β-galactosidase), an enzyme found in gastric juice. People who lack this enzyme after childhood cannot digest milk and are said to be lactose intolerant. Common symptoms of lactose intolerance include nausea, cramps, gas and diarrhoea, which begin about 30 minutes to 2 hours after eating or drinking foods containing lactose. Between 30 and 50 million Americans are lactose intolerant, with certain ethnic and racial populations being more widely affected than others; as many as 75 percent of all African-Americans and Native Americans and 90 percent of Asian-Americans are lactose intolerant. The condition is least common among persons of northern European descent. Enzymic methods for the measurement of lactose are well known and are generally based on the hydrolysis of lactose to D-galactose and D-glucose with β-galactosidase, followed by determination of either D-galactose or D-glucose.
    [Show full text]
  • Dismetabolic Cataracts
    ndrom Sy es tic & e G n e e n G e f T o Journal of Genetic Syndromes Cavallini et al., J Genet Syndr Gene Ther 2013, 4:7 h l e a r n a r p u DOI: 10.4172/2157-7412.1000165 y o J & Gene Therapy ISSN: 2157-7412 Case Report Open Access Dismetabolic Cataracts: Clinicopathologic Overview and Surgical Management with B-MICS Technique Cavallini GM1, Forlini M1, Masini C1, Campi L1, Chiesi C1, Rejdak R2 and Forlini C3* 1Institute of Ophthalmology, University of Modena, Modena, Italy 2Department of Ophthalmology, Medical University of Lublin, Lublin, Poland 3Department of Ophthalmology, “Santa Maria Delle Croci” Hospital, Ravenna, Italy Abstract Background: Dismetabolic cataract is a loss of lens transparency due to an insult to the nuclear or lenticular fibers, caused by a metabolic disorder. The lens opacification may occur early or later in life, and may be isolated or associated to particular syndromes. We describe some of these metabolic conditions associated with cataract formation, and in particular we report our experience with a patient affected by lathosterolosis that presented bilateral cataracts. Methods: Our patient was a 7-years-old little girl diagnosed with lathosterolosis at age 2 years, through gas cromatography/mass spectrometry method for plasma sterol profile that revealed a peak corresponding to cholest- 7-en-3β-ol (lathosterol). Results: The lens samples obtained during surgical removal with B-MICS technique were sent to the Department of Pathology and routinely processed and stained with haematoxylin-eosin and PAS; then, they were examined under a light microscope. Histological examination revealed lens fragments with the presence of fibers disposed in a honeycomb way, samples characterized by the presence of homogeneous eosinophilic lens fibers, and other fragments characterized by bulgy elements referable to cortical fibers with degenerative characteristics.
    [Show full text]
  • Fructose and Mannose in Inborn Errors of Metabolism and Cancer
    H OH metabolites OH Review Fructose and Mannose in Inborn Errors of Metabolism and Cancer Elizabeth L. Lieu †, Neil Kelekar †, Pratibha Bhalla † and Jiyeon Kim * Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, IL 60607, USA; [email protected] (E.L.L.); [email protected] (N.K.); [email protected] (P.B.) * Correspondence: [email protected] † These authors contributed equally to this work. Abstract: History suggests that tasteful properties of sugar have been domesticated as far back as 8000 BCE. With origins in New Guinea, the cultivation of sugar quickly spread over centuries of conquest and trade. The product, which quickly integrated into common foods and onto kitchen tables, is sucrose, which is made up of glucose and fructose dimers. While sugar is commonly associated with flavor, there is a myriad of biochemical properties that explain how sugars as biological molecules function in physiological contexts. Substantial research and reviews have been done on the role of glucose in disease. This review aims to describe the role of its isomers, fructose and mannose, in the context of inborn errors of metabolism and other metabolic diseases, such as cancer. While structurally similar, fructose and mannose give rise to very differing biochemical properties and understanding these differences will guide the development of more effective therapies for metabolic disease. We will discuss pathophysiology linked to perturbations in fructose and mannose metabolism, diagnostic tools, and treatment options of the diseases. Keywords: fructose and mannose; inborn errors of metabolism; cancer Citation: Lieu, E.L.; Kelekar, N.; Bhalla, P.; Kim, J. Fructose and Mannose in Inborn Errors of Metabolism and Cancer.
    [Show full text]
  • Galactosaemia in an Infant: Case Report F.V
    May 1999 EAST AFRICAN MEDICAL JOURNAL 28 1 East Atiican Medical Journal Vol. 76 No 5 May 1999 GALACTOSAEMIA IN AN INFANT: CASE REPORT F.V. Murila. MBChB. MMed, Lecturer, Department of Paediatrics and Child Health College of Health Sciences, University of Nairobi, P.O. Box 19676, Nairobi GALACTOSAEMIA IN AN INFANT: CASE REPORT F.V. MURILA SUMMARY Galactosaemia is a disorder of galactose metabolism in which raised levels of galactose and galactose-1-phosphate damage various organs. It is a very rare disease (incidence 1 in 60,000) and the diagnosis is often missed, leading to poor prognosis. A case of clinical galactosaemia that was diagnosed at the age of 11 months is reported. It is important to be aware of this condition as early treatment may prevent some of the complications. INTRODUCTION Assay of the respective enzyme in the red blood cell, white blood cell and fibroblasts shows a deficiency Galactosaemia is a very rare disorder of galactose of the enzyme(4). Red blood cells (RBC) lactose-l- metabolism whose mode of inheritance is autosomal phosphate levels are high(2). recessive(1). It is characterised by a deficiency of any Treatment consists of dietary restriction of lactose. of three enzymes. These are galactokinase, galactose- Inspite of strict lactose restriction, however, neurological I-phosphate uridyl transferase (GALT) and uridyl and gonadal damage are relentlessly progressive(2,5). diphosphogalactose-4-epimerase. A deficiency of galactokinase leads to an increase in serum galactose CASE REPORT - with subsequent galactosuria The excess galactose is converted to galactitol which leads to cataract formation. J.M.was well until the age of three months when he Intelligence is spared.
    [Show full text]