Abstract
Discordance between clinical phenotype and the level of a mutant enzyme activity may reflect differences between enzyme function in vivo and that measured by the customary enzyme assays on cell extracts. In the present study, the conversion of hypoxanthine to phosphorylated products was measured in intact skin fibroblasts and in cell extracts from seven patients with mutant hypoxanthine-guanine phosphoribosyltransferase (HPRT) and six control subjects. The patient's phenotypes ranged from asymptomatic hyperuricemia to the Lesch-Nyhan syndrome. Although there was a general correlation between the HPRT activity in cell extracts assayed by the usual methods and the function of the purine salvage pathway in patients, as reflected by urinary oxypurine excretion, there were notable exceptions. A more accurate appraisal of the functioning of the pathway at the cellular level is achieved by measuring the conversion of substrate to product in the intact cell at physiological concentrations of substrates, activators, and product and metabolite inhibitors, and in a physiological ionic environment. In one of the seven patients, the standard enzyme assay indicated normal function, whereas measurements in the intact cell exposed severe dysfunction of the salvage system. In another, the standard assay suggested a severe deficiency not evident in the intact cell or in the patient.
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- ATKINSON M. R., MURRAY A. W. INHIBITION OF PRUINE PHOSPHORIBOSYLTRANSFERASES OF EHRLICH ASCITES-TUMOUR CELLS BY 6-MERCAPTOPURINE. Biochem J. 1965 Jan;94:64–70. doi: 10.1042/bj0940064. [DOI] [PMC free article] [PubMed] [Google Scholar]
- BRESNICK E., KARJALA R. J. END-PRODUCT INHIBITION OF THYMIDINE KINASE ACTIVITY IN NORMAL AND LEUKEMIC HUMAN LEUKOCYTES. Cancer Res. 1964 Jun;24:841–846. [PubMed] [Google Scholar]
- Benke P. J., Herrick N. Azaguanine-resistance as a manifestation of a new form of metabolic overproduction of uric acid. Am J Med. 1972 Apr;52(4):547–555. doi: 10.1016/0002-9343(72)90046-0. [DOI] [PubMed] [Google Scholar]
- Benke P. J., Herrick N., Hebert A. Hypoxanthine-guanine phosphoribosyltransferase variant associated with accelerated purine synthesis. J Clin Invest. 1973 Sep;52(9):2234–2240. doi: 10.1172/JCI107409. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dancis J., Yip L. C., Cox R. P., Piomelli S., Balis M. E. Disparate enzyme activity in erythocytes and leukocytes. A variant of hypoxanthine phosphoribosyl-transferase deficiency with an unstable enzyme. J Clin Invest. 1973 Aug;52(8):2068–2074. doi: 10.1172/JCI107391. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Delbarre F., Cartier P., Auscher C., de Géry A., Hamet M. Gouttes enzymopathiques. Dyspurinies par déficit en hypoxanthine-guanine-phosphoribosyltransférase. Fréquence et caractères cliniques de L'anenzymose. Presse Med. 1970 Mar 28;78(16):729–734. [PubMed] [Google Scholar]
- Fox I. H., Kelley W. N. Phosphoribosylpyrophosphate in man: biochemical and clinical significance. Ann Intern Med. 1971 Mar;74(3):424–433. doi: 10.7326/0003-4819-74-3-424. [DOI] [PubMed] [Google Scholar]
- Henderson J. F., Brox L. W., Kelley W. N., Rosenbloom F. M., Seegmiller J. E. Kinetic studies of hypoxanthine-guanine phosphoribosyltransferase. J Biol Chem. 1968 May 25;243(10):2514–2522. [PubMed] [Google Scholar]
- Kaufman J. M., Greene M. L., Seegmiller J. E. Urine uric acid to creatinine rtio--a screening test for inherited disorders of purine metabolism. Phosphoribosyltransferase (PRT) deficiency in X-linked cerebral palsy and in a variant of gout. J Pediatr. 1968 Oct;73(4):583–592. doi: 10.1016/s0022-3476(68)80274-4. [DOI] [PubMed] [Google Scholar]
- Kelley W. N., Greene M. L., Rosenbloom F. M., Henderson J. F., Seegmiller J. E. Hypoxanthine-guanine phosphoribosyltransferase deficiency in gout. Ann Intern Med. 1969 Jan;70(1):155–206. doi: 10.7326/0003-4819-70-1-155. [DOI] [PubMed] [Google Scholar]
- Kelley W. N., Rosenbloom F. M., Henderson J. F., Seegmiller J. E. A specific enzyme defect in gout associated with overproduction of uric acid. Proc Natl Acad Sci U S A. 1967 Jun;57(6):1735–1739. doi: 10.1073/pnas.57.6.1735. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kogut M. D., Donnell G. N., Nyhan W. L., Sweetman L. Disorder of purine metabolism due to partial deficiency of hypoxanthine-guanine phosphoribosyltransferase. A study of a family. Am J Med. 1970 Feb;48(2):148–161. doi: 10.1016/0002-9343(70)90111-7. [DOI] [PubMed] [Google Scholar]
- LESCH M., NYHAN W. L. A FAMILIAL DISORDER OF URIC ACID METABOLISM AND CENTRAL NERVOUS SYSTEM FUNCTION. Am J Med. 1964 Apr;36:561–570. doi: 10.1016/0002-9343(64)90104-4. [DOI] [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
- Nyhan W. L. The Lesch-Nyhan syndrome. Annu Rev Med. 1973;24:41–60. doi: 10.1146/annurev.me.24.020173.000353. [DOI] [PubMed] [Google Scholar]
- Rubin C. S., Balis M. E., Piomelli S., Berman P. H., Dancis J. Elevated AMP pyrophosphorylase activity in congenital IMP pyrophosphorylase deficiencey (Lesch-Nyhan disease). J Lab Clin Med. 1969 Nov;74(5):732–741. [PubMed] [Google Scholar]
- Seegmiller J. E., Rosenbloom F. M., Kelley W. N. Enzyme defect associated with a sex-linked human neurological disorder and excessive purine synthesis. Science. 1967 Mar 31;155(3770):1682–1684. doi: 10.1126/science.155.3770.1682. [DOI] [PubMed] [Google Scholar]
- Snyder F. F., Henderson J. F., Cook D. A. Inhibition of purine metabolism--computer-assisted analysis of drug effects. Biochem Pharmacol. 1972 Sep 1;21(17):2351–2357. doi: 10.1016/0006-2952(72)90386-3. [DOI] [PubMed] [Google Scholar]
- Sorensen L. B., Benke P. J. Biochemical evidence for a distinct type of primary gout. Nature. 1967 Mar 18;213(5081):1122–1123. doi: 10.1038/2131122b0. [DOI] [PubMed] [Google Scholar]
- WAYMOUTH C. Rapid proliferation of sublines of NCTC clone 929 (strain L) mouse cells in a simple chemically defined medium (MB 752/1). J Natl Cancer Inst. 1959 May;22(5):1003–1017. doi: 10.1093/jnci/22.5.1003. [DOI] [PubMed] [Google Scholar]
- Yü T. F., Balis M. E., Krenitsky T. A., Dancis J., Silvers D. N., Elion G. B., Gutman A. B. Rarity of X-linked partial hypoxanthine-guanine phosphoribosyltransferase deficiency in a large gouty population. Ann Intern Med. 1972 Feb;76(2):255–264. doi: 10.7326/0003-4819-76-2-255. [DOI] [PubMed] [Google Scholar]