Title : Effect of divalent cations on NADH-dependent and NADPH-dependent cytochrome b5 reduction by hepatic microsomes.

Pub. Date : 1990 Aug 1

PMID : 2369123






6 Functional Relationships(s)
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1 The reduction of exogenous cytochrome b5 by microsomes was low at 1.2 microM cytochrome b5 (3.9 or 2.7 nmol/min/mg protein, respectively, with NADH or NADPH). NAD cytochrome b5 type A Homo sapiens
2 The reduction of exogenous cytochrome b5 by microsomes was low at 1.2 microM cytochrome b5 (3.9 or 2.7 nmol/min/mg protein, respectively, with NADH or NADPH). NAD cytochrome b5 type A Homo sapiens
3 MgCl2 also stimulated cytochrome b5 reduction with a EC50 value of 1.0 mM in the NADH system or 0.6 mM in the NADPH system. NAD cytochrome b5 type A Homo sapiens
4 The Km value for cytochrome b5 was decreased and the Vmax was increased by calcium with either the NADH- or the NADPH-dependent system. NAD cytochrome b5 type A Homo sapiens
5 In the presence of Triton X-100, divalent cations were inhibitory in NADH-dependent cytochrome b5 reduction, and in contrast, stimulative in NADPH-dependent reaction. NAD cytochrome b5 type A Homo sapiens
6 These findings suggest that the activation of cytochrome b5 reduction by divalent cations in the NADH system is mainly due to an increasing accessibility of the substrate, and in the NADPH system, in addition to this, a direct effect of divalent cations on NADPH-cytochrome P450 reductase is also involved. NAD cytochrome b5 type A Homo sapiens