Biomaterial Database

Contribution of human CYP3A subfamily members to the 6-hydroxylation of chlorzoxazone. 1997

J C Gorski, and D R Jones, and S A Wrighton, and S D Hall

Department of Medicine, Indiana University, Indianapolis 46202, USA.

1. The capability of human CYPs other than 2E1 to catalyse the formation of 6-hydroxychlorzoxazone (6OHCHZ) was examined in vitro using human liver microsomes. 2. 4-Methylpyrazole, diethyldithiocarbamate (DDC), and rabbit anti-human CYP2E1 antibodies reduced chlorzoxazone 6-hydroxylase activity by 60, 60 and 50% respectively. The rate of formation of 6OHCHZ by DDC-treated microsomes was reduced further by the 3A inhibitors midazolam, troleandomycin and gestodene and increased by alpha-naphtholavone, a 3A4 stimulator. 3. Following preincubation with DDC there were significant correlations (p < 0.05) between the residual CHZ 6-hydroxylase activity and immunoquantified CYP3A levels, and corresponding activities (e.g. midazolam 1'-hydroxylation). Rabbit anti-human CYP3A antibodies alone and in combination with DDC reduced the formation of 6OHCHZ by 47 and 62", respectively. 4. cDNA expressed CYP3A4, 2E1 and 2D6 exhibited comparable CHZ 6-hydroxylase activity. CHZ modulated 3A4 activity as reflected by midazolam 1'-hydroxylase and 4-hydroxylase activities. 5. CYP3A may make a significant contribution to CHZ 6-hydroxylation and therefore caution should be exercized when chlorzoxazone is employed as a specific 2E1 probe in vitro and in vivo.

UI	MeSH Term	Description	Entries
D007527	Isoenzymes	Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.	Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D009125	Muscle Relaxants, Central	A heterogeneous group of drugs used to produce muscle relaxation, excepting the neuromuscular blocking agents. They have their primary clinical and therapeutic uses in the treatment of muscle spasm and immobility associated with strains, sprains, and injuries of the back and, to a lesser degree, injuries to the neck. They have been used also for the treatment of a variety of clinical conditions that have in common only the presence of skeletal muscle hyperactivity, for example, the muscle spasms that can occur in MULTIPLE SCLEROSIS. (From Smith and Reynard, Textbook of Pharmacology, 1991, p358)	Centrally Acting Muscle Relaxants,Central Muscle Relaxants,Relaxants, Central Muscle
D010089	Oxidoreductases, N-Demethylating		N-Demethylase,N-Demethylases,Oxidoreductases, N Demethylating,Demethylating Oxidoreductases, N,N Demethylase,N Demethylases,N Demethylating Oxidoreductases,N-Demethylating Oxidoreductases
D002753	Chlorzoxazone	A centrally acting central muscle relaxant with sedative properties. It is claimed to inhibit muscle spasm by exerting an effect primarily at the level of the spinal cord and subcortical areas of the brain. (From Martindale, The Extra Pharmacopoea, 30th ed, p1202)	Paraflex,Parafon,Parafon Forte DSC
D002851	Chromatography, High Pressure Liquid	Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.	Chromatography, High Performance Liquid,Chromatography, High Speed Liquid,Chromatography, Liquid, High Pressure,HPLC,High Performance Liquid Chromatography,High-Performance Liquid Chromatography,UPLC,Ultra Performance Liquid Chromatography,Chromatography, High-Performance Liquid,High-Performance Liquid Chromatographies,Liquid Chromatography, High-Performance
D003577	Cytochrome P-450 Enzyme System	A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.	Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450
D004791	Enzyme Inhibitors	Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.	Enzyme Inhibitor,Inhibitor, Enzyme,Inhibitors, Enzyme
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man