Decreased S-adenosylhomocysteine hydrolase in inborn errors of purine metabolism.

A deficiency of erythrocyte S-adenosylhomocysteine hydrolase has been confirmed in three patients with adenosine deaminase deficiency. In addition, erythrocyte S-adenosylhomocysteine hydrolase activity was decreased by 85% in three patients with purine nucleoside phosphorylase deficiency and by 57% in 15 patients with hypoxanthine-guanine phosphoribosyltransferase deficiency. Cultured diploid fibroblasts from these patients were normal. Besides deoxyadenosin, no compound known to accumulate in these disorders caused S-adenosylhomocysteine hydrolase inactivation. S-adenosylhomocysteine hydrolase had a normal half-life in the erythrocytes from two patients with Lesch-Nyhan syndrome. A secondary deficiency of S-adenosylhomocysteine hydrolase may accompany a number of inborn errors of purine metabolism. Whether this enzyme deficiency contributes to the molecular pathology of these diseases is not known.