S-Adenosylhomocysteine Hydrolase Activity in Defects of Enzymes of Purine Metabolism and Inhibition by Various Purine Compounds
S-adenosylhomocysteine hydrolase (SAH hydrolase, E.0.3.3.1.1) reversibly catalyses the reaction: S-Adenosyl-L-homocysteine (SAH) + H20 ⇌ Adenosine + L-Homocysteine. A decrease in SAH hydrolase activity is observed in inherited Adenosine deaminase (ADA) deficiency with Severe Combined Immunodeficiency (SCID) (1–2). This decrease is thought to be due to inhibition of SAH hydrolase by 2′-deoxyadenosine (3) Which accumulates in ADA deficiency (4, 5). Recently Kaminska and Fox (6) showed that SAH hydrolase activity is significantly lowered in two other enzymatic deficiencies of purine metabolism. This prompted us to determine SAH hydrolase activity in Hypoxanthine-Guanine-phosphoribosyltransferase (HGPRT) deficiency with Lesch-Nyhan syndrome, ADA deficiency with and without immunodeficiency, and total Adenine-phosphoribosyltrans-ferase (APRT) deficiency. We also studied inhibitory effect of some adenine compounds especially 5′-deoxy-5′-methylthioadenosine(MTA) (3, 7) which is an inhibitor of lymphocyte blastogenesis (8).
KeywordsAdenosine Deaminase Severe Combine Immunodeficiency Purine Metabolism Orotic Acid Orotate Phosphoribosyltransferase
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