N-methylcarbazole metabolism by a purified isozyme of rat liver microsomal cytochrome P-450: membrane effects and autocatalytic inactivation

Thesis/Dissertation · Tue Jan 01 00:00:00 EST 1985

OSTI ID:6105353

Gurka, D P

The catalytic properties of purified cytochrome P-450b, the major isozyme found in hepatic microsomes from phenobarbital-pretreated rats, for the metabolism of N-methylcarbazole (NMC) were analyzed in two membranous systems in order to investigate membrane bilayer-dependent parameters. Incorporation of the enzymes of the monoxygenase system into bilayer liposomal vesicles composed of total microsomal lipid had no effect on the rates or regioselectivity of the mono-hydroxylation of the substrate when compared to the same enzymes reconstituted in a soluble system with small amounts of dilauroylphosphatidylcholine (DLPC). The membranous system exhibited K/sub m/ values of NMC which were 4-5 times higher than the non-vesicular system. The rapid decline in the rates of NMC metabolism by cytochrome P-450b during catalysis suggested enzyme inactivation during substrate processing. Radiolabel from (methyl-/sup 14/C)NMC was incorporated into the P-450b apoprotein as a result of enzyme turnover co-incident with the loss of enzyme activity. NMC-stimulated NADPH oxidation by the reconstituted enzyme system containing DLPC was biophasic, with a slow rate preceding a two-fold higher rate. Carbazole and some N-substituted derivatives were unique in stimulating this unusual oxidation.

• Research Organization: Northwestern Univ., Evanston, IL (USA)
• OSTI ID: 6105353
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CARBAZOLES
METABOLISM
CARBON 14 COMPOUNDS
MIXED-FUNCTION OXIDASES
INACTIVATION
KINETICS
CATALYSIS
CYTOCHROMES
LIPIDS
LIPOSOMES
MICROSOMES
PHOSPHOLIPIDS
RATS
ANIMALS
AROMATICS
AZAARENES
AZOLES
CELL CONSTITUENTS
ENZYMES
ESTERS
HETEROCYCLIC COMPOUNDS
LABELLED COMPOUNDS
MAMMALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANOIDS
OXIDOREDUCTASES
OXYGENASES
PIGMENTS
PROTEINS
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques