The enzyme catalysing the hydroxylation of ecdysone to 20-hydroxyecdysone, ecdysone 20-mono-oxygenase (EC 1.14.99.22), was investigated in the Malpighian tubules of fifth-instar locusts, Schistocerca gregaria. Enzyme activity was optimal at 35 degrees C and pH 6.8-8.0. Under these conditions the mono-oxygenase exhibited an apparent Km for ecdysone of 7.1 X 10(-7) M, a maximal specific activity ...

The form of liver microsomal cytochrome P-450 induced by chronic administration of ethanol to rabbits, designated as P-450ALC or P-450 isozyme 3a, has been purified to homogeneity as judged by several criteria, including NH2- and COOH-terminal amino acid sequence determination. The reconstituted alcohol-P-450 oxygenase (APO) system containing P-450ALC and NADPH-cytochrome P-450 reductase cataly...

Reductive metabolism of carcinogenic 1-nitropyrene by rat liver microsomes and reconstituted cytochrome P-450 systems was investigated. Under the nitrogen atmosphere, 1-aminopyrene was the only detected metabolite of 1-nitropyrene. The reductase activity in liver 105,000 X g supernatant fraction was ascribed to DT-diaphorase, aldehyde oxidase, and other unknown enzyme(s) from the results of cof...

An intraperitoneal dose of CS(2) (500mg/kg) to male rats resulted in loss of liver microsomal mixed-function-oxidase activity (85% loss of biphenyl 4-hydroxylase), followed by denaturation of liver cytochrome P-450 to cytochrome P-420, and degradative loss of both cytochromes (50% loss). Losses of NADPH-cytochrome c reductase (20%) and cytochrome b(5) were considerably less. Intraperitoneal adm...

Two unique forms of cytochrome P-450 (P-450), designated NMa and NMb, were recently isolated in this laboratory from nasal microsomes of rabbits. In the present study, polyclonal antibodies to the purified nasal cytochromes were prepared. Immunochemical analysis with specific rabbit anti-NMa and sheep anti-NMb antibodies indicated that P-450 isozymes identical to or having a high structural hom...

Using the stereospecific metabolism of (+)- and (-)-bufuralol and (+)- and (-)-metoprolol as model reactions, we have characterized the enzymic deficiency of the debrisoquine/sparteine-type polymorphism by comparing kinetic data of subjects in vivo with their microsomal activities in vitro and with reconstituted activities of cytochrome P-450 isozymes purified from human liver. The metabolism o...

Cholesterol side chain cleavage has been shown to be dependent on the electron carrier chain involving a cytochrome P-450 reductase system, flavoprotein and nonheme iron-protein of the ferredoxin type, and the oxygen-activating cytochrome P-450. The reaction is markedly inhibited by carbon monoxide. The cytochrome oxidase system inhibits the cleavage reaction by diverting the flow of electrons ...

chrome P-450 concentration shows the disappearance to be loss of the active conformation of the enzyme rather than inhibition of an enzyme assay, as is employed with most other enzymes. No cytochrome P-450 could be detected by our methods in yeast strains N.C.Y.C. 73,74,366,379,533,686,692 and 716. A respiratory-deficient mutant of yeast (N.C.Y.C. 240) was shown to produce cytochrome P-450 even...

The 02, CO, and alkyl isocyanide-binding properties of a variety of vertebrate and invertebrate heme proteins have been compared in detail to those of protoheme mOn0-3-( 1-imidazoy1)-propylamide monomethyl ester in aqueous suspensions of soap micelles. The proteins examined include: cytochrome P-450,,, from Pseudomonasputida, beef heart cytochrome c oxidase, yeast cytochrome c peroxidase, a and...