title: Affinity labeling of rat liver microsomal NADH-5 alpha-reductase with a nucleoside analogue.
abstract: A time dependent irreversible loss of rat liver microsomal NADH-5 alpha-reductase activity is caused by incubation of microsomes with the nucleoside 5'-p-fluorosulfonylbenzoyladenosine (FSA). The decrease of activity is dependent on FSA concentration and shows first order kinetics. Presence of NADH partially stabilizes the NADH-5 alpha-reductase. Thioglycerol present before incubation prevents loss of activity, and stops decrease of activity when added during incubation. NADPH-5 alpha-reductase (E.C. 1.3.1.4) and NADPH-cytochrome c reductase (E.C. 1.6.2.4) are not influenced while NADH-cytochrome c reductase (E.C. 1.6.99.3) is inhibited by FSA. Evidently FSA causes inactivation of the enzymes by binding to the NADH-binding site. Affinity labeling by FSA thus clearly distinguishes between NADH- and NADPH-dependent 5 alpha-reductases from rat liver microsomes.
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism; D058891:5-alpha Reductase Inhibitors; D000241:Adenosine / Q000031:analogs & derivatives*; D000345:Affinity Labels; D000818:Animals; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology*; D009245:NADH Dehydrogenase / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D058891:5-alpha Reductase Inhibitors; D000345:Affinity Labels; C010959:5'-(4-fluorosulfonylbenzoyl)adenosine; D010088:Oxidoreductases; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; D009251:NADPH-Ferrihemoprotein Reductase; D009245:NADH Dehydrogenase; D000241:Adenosine