title: Affinity modification of NADPH-cytochrome P-450 reductase.
abstract: The active centre of NADPH-cytochrome P-450 reductase contains the lysine residue essential for catalytic activity. Chemical modification of epsilon-amino group of this lysine residue is the subject of the present study. To modify the epsilon-amino group, we have employed the periodate-oxidized NADP+ and NAD+ (o-NAD(P]. The both reagents have appeared to be the competitive inhibitors of NADPH-cytochrome P-450 reductase (Ki for o-NADP approximately 10 microM, Ki for o-NAD greater than 100 microM). However, o-NADP has not a covalency bond with reductase, whilst o-NAD modifies the reductase at the binding site of NADPH. A protective effect of NADP+ and the labeling extent close to unity (0.7) at deep reductase inactivation indicate the affinity type of this modification. Different results of reductase modification by either o-NADP or o-NAD may be due to the difference in the structures of the analogs bound to the enzyme active site.
mesh_terms: D000818:Animals; D001665:Binding Sites; D006834:Hydrazines / Q000494:pharmacology; D007700:Kinetics; D008239:Lysine; D008862:Microsomes, Liver / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D051381:Rats
chemical_list: D006834:Hydrazines; C029424:hydrazine; D009251:NADPH-Ferrihemoprotein Reductase; D008239:Lysine