RT Journal Article SR Electronic T1 Studies on the Relationship between the Effects of Various Substances on Absorption Spectrum of Cytochrome P-450 and the Reduction of p-Nitrobenzoate by Mouse Liver Microsomes JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 123 OP 130 VO 5 IS 2 A1 HENRY A. SASAME A1 JAMES R. GILLETTE YR 1969 UL http://molpharm.aspetjournals.org/content/5/2/123.abstract AB The reduction of p-nitrobenzoate by an NADPH-dependent enzyme in liver microsomes is presumably mediated by cytochrome P-450. The reaction is inhibited by substances which cause type II spectral changes in liver microsomes, but not by those which cause type I spectral changes. Type II substances inhibit only about 50% of the nitroreductase activity in liver microsomes. The apparent Ki values for the inhibition of p-nitrobenzoate reduction are approximately double the K[unknown], values of the various type II substances studied. The evidence suggests that type II substances inhibit p-nitrobenzoate reduction by slowing the rate of cytochrome P-450 reduction.