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

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Abstract
The effects of S-adenosylhomocysteine and S-adenosylmethionine on some purine- and pyrimidine-metabolizing systems were examined. Both compounds were capable of acting as relatively good inhibitors of adenosine deaminase [EC 3.5.4.4 (calf intestine)], nucleoside phosphorylase [EC 2.4.2.1 (calf spleen)] and adenylate deaminase [EC 3.5.4.6 (rabbit muscle)] activities, but as relatively poor inhibitors of myokinase [EC 2.7.4.3 (hog muscle)] and nucleoside monophosphate kinase [EC 2.7.4.4]. The inhibitory effects were freely reversible. 5''-Nucleotidase [EC 3.1.3.5 (Crotalus atrox venom)] orotidine 5''-phosphate and phosphodiesterase [EC 3.1.4.1 (beef heart)] were unaffected. Nucleoside phosphorylase was competitively inhibited by both compounds, whereas mixed inhibitory effects occurred with adenosine deaminase.