title: Biodiversity of the P450 catalytic cycle: yeast cytochrome b5/NADH cytochrome b5 reductase complex efficiently drives the entire sterol 14-demethylation (CYP51) reaction.
abstract: The widely accepted catalytic cycle of cytochromes P450 (CYP) involves the electron transfer from NADPH cytochrome P450 reductase (CPR), with a potential for second electron donation from the microsomal cytochrome b5/NADH cytochrome b5 reductase system. The latter system only supported CYP reactions inefficiently. Using purified proteins including Candida albicans CYP51 and yeast NADPH cytochrome P450 reductase, cytochrome b5 and NADH cytochrome b5 reductase, we show here that fungal CYP51 mediated sterol 14alpha-demethylation can be wholly and efficiently supported by the cytochrome b5/NADH cytochrome b5 reductase electron transport system. This alternative catalytic cycle, where both the first and second electrons were donated via the NADH cytochrome b5 electron transport system, can account for the continued ergosterol production seen in yeast strains containing a disruption of the gene encoding CPR.
authors.affiliation: Institute of Biological Sciences, University of Wales Aberystwyth, UK.
authors.forename: D C
authors.initials: DC
authors.lastname: Lamb
authors.forename: D E
authors.initials: DE
authors.lastname: Kelly
authors.forename: N J
authors.initials: NJ
authors.lastname: Manning
authors.forename: M A
authors.initials: MA
authors.lastname: Kaderbhai
authors.forename: S L
authors.initials: SL
authors.lastname: Kelly
mesh_terms: D002176:Candida albicans / Q000201:enzymology*; D002384:Catalysis; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism* / Q000502:physiology*; D003579:Cytochrome Reductases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D042966:Cytochrome-B(5) Reductase; D015786:Cytochromes b5 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D007700:Kinetics; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase; D010088:Oxidoreductases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D058886:Sterol 14-Demethylase; D013997:Time Factors
chemical_list: D011994:Recombinant Proteins; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D009247:NADH, NADPH Oxidoreductases; D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase; D009251:NADPH-Ferrihemoprotein Reductase