Partial deficiency of hypoxanthine-guanine phosphoribosyltransferase with reduced affinity for PP-ribose-P in four related males with gout |
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| Authors: | F F Snyder A E Chudley P M MacLeod R J Carter E Fung J K Lowe |
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| Institution: | (1) Department of Pediatrics, Faculty of Medicine, University of Calgary, T2N 4N1 Calgary, Alberta, Canada;(2) Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, T2N 4N1 Calgary, Alberta, Canada;(3) Health Sciences Center, Children's Hospital, R3E 0W1 Winnipeg, Manitoba, Canada;(4) Department of Pediatrics, Division of Medical Genetics, Queen's University, K7L 3N6 Kingston, Ontario, Canada |
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| Abstract: | Summary A family is described in which four affected males, spanning two generations, have hyperuricemia and gout accompanied by hematuria but are without severe neurologic involvement. The affected males were found to have markedly reduced levels of erythrocytic hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity; these were 5–12% with hypoxanthine and 0.5–3% with guanine as compared to controls. Erythrocytic adenine phosphoribosyltransferase (APRT) was approximately three-fold elevated in the affected individuals.The residual HGPRT activity in affected males enabled characterization of some of the properties of this mutation. The apparent Michaelis constants (km) for both hypoxanthine and guanine were essentially unchanged, whereas the km for PP-ribose-P was approximately 10–20-fold elevated for all four affected males. The enzyme was more sensitive to product inhibition by IMP and GMP than controls, and exhibited greater thermal lability at 65°C than found with control lysates. |
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