Role of 5'-nucleotidase in thiopurine metabolism: enzyme kinetic profile and association with thio-GMP levels in patients with acute lymphoblastic leukemia during 6-mercaptopurine treatment.

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Publication year
2005Source
Clinica Chimica Acta, 361, 1-2, (2005), pp. 95-103ISSN
Publication type
Article / Letter to editor

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Organization
Paediatrics - OUD tm 2017
NCMLS
Former Organization
NCMLS 2a
Journal title
Clinica Chimica Acta
Volume
vol. 361
Issue
iss. 1-2
Page start
p. 95
Page end
p. 103
Subject
IGMD 3: Genomic disorders and inherited multi-system disorders; NCMLS 2: Immune Regulation; ONCOL 1: Hereditary cancer and cancer-related syndromes; ONCOL 2: Age-related aspects of cancer; ONCOL 3: Translational research; UMCN 1.4: Immunotherapy, gene therapy and transplantationAbstract
Thiopurines are used for treatment of several diseases. Cytotoxicity is caused by the derived compounds 6-thioguanine nucleotides (TGNs) and methyl-6-thioinosine monophosphate (methylthio-IMP). The 6-thiopurine mononucleotides 6-thio-IMP (thio-IMP), 6-thio-GMP (thio-GMP) and methylthio-IMP can be catabolized by purine 5'-nucleotidase. It has been shown that the various 5'-nucleotidases are key enzymes for (6-thio)-purine metabolism. We aimed to investigate whether the overall 5'-nucleotidase (5'NT) activity is correlated with the efficacy and toxicity of 6-thiopurine nucleotides. Substrate affinity of 5'NT for IMP, GMP, AMP, thio-IMP, thio-GMP and methylthio-IMP was studied in human lymphocytes. For each of the substrates, the pH for optimal overall enzyme activity has been determined at a pH range between 6 and 10. At the optimal pH, assays were performed to establish Km and Vmax values. Optimal pH values for the various substrates were between 7 and 8.5. Km values ranged from 33 to 109 microM, Vmax ranged from 3.99 to 19.5 nmol/10(6) peripheral mononuclear cells (pMNC) h, and Vmax/Km ratios ranged from 105 to 250. The results did not show a distinct preference of 5'NT activity for any of the tested thiopurine nucleotides. The enzyme kinetic studies furthermore revealed substrate inhibition by thio-IMP and thio-GMP as a substrate. Inhibition by thio-GMP also seems to occur in patients treated with 6-mercaptopurine (6 MP); subsequently, this may lead to toxicity in these patients.
This item appears in the following Collection(s)
- Academic publications [227901]
- Electronic publications [107370]
- Faculty of Medical Sciences [86237]
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