The effects of S-adenosylhomocysteine and S-adenosylmethionine on some purine- and pyrimidine-metabolizing systems.

The effects of S-adenosylhomocysteine and S-adenosylmethionine on some purine- and pyrimidine-metabolizing systems have been examined. Both compounds were capable of acting as relatively good inhibitors of adenosine deaminase, nucleoside phosphorylase, and adenylate deaminase activities but as relatively poor inhibitors of myokinase and nucleoside monophosphate kinase. The inhibitory effects were freely reversible. 5'-Nucleotidase, orotidine 5'- phosphate, and phosphodiesterase were unaffected. Nucleoside phosphorylase was competitively inhibited by both compounds, whereas mixed inhibitory effects occurred with adenosine deaminase.