Biomaterial Database

Cytochrome P-450-dependent 14 alpha-demethylation of lanosterol in Candida albicans. 1989

C A Hitchcock, and S B Brown, and E G Evans, and D J Adams

Department of Microbiology, University of Leeds, U.K.

A novel assay for cytochrome P-450-dependent 14 alpha-sterol demethylase of the important opportunistic fungal pathogen, Candida albicans, is described. The enzyme was assayed in microsomal preparations (microsomes) by measuring the incorporation of [14C]lanosterol into (4,14)-desmethylated sterols. The efficacy of different cell-breakage methods was compared; desmethylated-sterol biosynthesis was maximal when cells were broken with a Braun disintegrator. The solubilization of [14C]lanosterol with detergent in the assay system was essential for enzyme activity, which was enhanced considerably when microsomes were gassed with O2. Under these conditions, there was a reciprocal relationship between the amount of radioactivity incorporated into desmethylated sterols and that lost from lanosterol. The major radiolabelled desmethylated sterol was ergosterol. The enzyme had an apparent Km of 52.73 +/- 2.80 microM and an apparent Vmax of 0.84 +/- 0.14 nmol/min per mg of protein (n = 3). Enzyme activity was decreased greatly when microsomes were treated with CO or the triazole antifungal ICI 153066.

UI	MeSH Term	Description	Entries
D008861	Microsomes	Artifactual vesicles formed from the endoplasmic reticulum when cells are disrupted. They are isolated by differential centrifugation and are composed of three structural features: rough vesicles, smooth vesicles, and ribosomes. Numerous enzyme activities are associated with the microsomal fraction. (Glick, Glossary of Biochemistry and Molecular Biology, 1990; from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)	Microsome
D010088	Oxidoreductases	The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)	Dehydrogenases,Oxidases,Oxidoreductase,Reductases,Dehydrogenase,Oxidase,Reductase
D002176	Candida albicans	A unicellular budding fungus which is the principal pathogenic species causing CANDIDIASIS (moniliasis).	Candida albicans var. stellatoidea,Candida stellatoidea,Dematium albicans,Monilia albicans,Myceloblastanon albicans,Mycotorula albicans,Parasaccharomyces albicans,Procandida albicans,Procandida stellatoidea,Saccharomyces albicans,Syringospora albicans
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
D013261	Sterols	Steroids with a hydroxyl group at C-3 and most of the skeleton of cholestane. Additional carbon atoms may be present in the side chain. (IUPAC Steroid Nomenclature, 1987)	Sterol
D058886	Sterol 14-Demethylase	An NADPH-dependent P450 enzyme that plays an essential role in the sterol biosynthetic pathway by catalyzing the demethylation of 14-methyl sterols such as lanosterol. The enzyme acts via the repeated hydroxylation of the 14-methyl group, resulting in its stepwise conversion into an alcohol, an aldehyde and then a carboxylate, which is removed as formic acid. Sterol 14-demethylase is an unusual cytochrome P450 enzyme in that it is found in a broad variety of organisms including ANIMALS; PLANTS; FUNGI; and protozoa.	Sterol 14-Demethylases,CYP51 Cytochrome P-450,Cytochrome P-450 CYP51,Eburicol 14 alpha-Demethylase,Eburicol 14alpha-Demethylase,Lanosterol 14 alpha-Demethylase,Obtusifoliol 14alpha-Demethylase,Sterol 14-alpha-Demethylase,14 alpha-Demethylase, Eburicol,14 alpha-Demethylase, Lanosterol,14-Demethylase, Sterol,14-Demethylases, Sterol,14-alpha-Demethylase, Sterol,14alpha-Demethylase, Eburicol,14alpha-Demethylase, Obtusifoliol,CYP51 Cytochrome P 450,CYP51, Cytochrome P-450,Cytochrome P 450 CYP51,Cytochrome P-450, CYP51,Eburicol 14 alpha Demethylase,Eburicol 14alpha Demethylase,Lanosterol 14 alpha Demethylase,Obtusifoliol 14alpha Demethylase,P-450 CYP51, Cytochrome,P-450, CYP51 Cytochrome,Sterol 14 Demethylase,Sterol 14 Demethylases,Sterol 14 alpha Demethylase