title: Cytochrome P450 2C9 is responsible for hydroxylation of the naphthoquinone antimalarial drug 58C80 in human liver.
abstract: 2-(4-t-Butylcyclohexyl)-3-hydroxy-1,4-naphthoquinone (58C80) is an experimental naphthoquinone antimalarial drug which undergoes extensive alky hydroxylation in man. By means of purification, N-terminal amino acid sequencing and inhibition by antibodies and sulfaphenazole, we have identified the form of cytochrome P450 primarily responsible for 58C80 hydroxylation in human liver, P450hB20-27, to be a member of the P450 2C9 subfamily. P450hB20-27 is a low-spin haemoprotein with molecular mass 54 kDa. 58C80 hydroxylation in human liver microsomes was dependent on either NADPH or NADH, with the activity supported by NADH being 35% of that supported by NADPH. With purified P450hB20-27 cytochrome b5 stimulated the NADH-dependent activity 8-fold but inhibited the NADPH-dependent activity by 30%. 58C80 is a novel substrate structure for human P450 2C and these results significantly broaden the range of drugs which have been directly shown (i.e. using a purified enzyme as opposed to expressed cDNA) to be metabolized by human P450 2C forms that are incontrovertibly expressed in human liver in vivo.
authors.affiliation: Department of Biomedical Sciences, University of Aberdeen, Marischal College, U.K.
authors.forename: R J
authors.initials: RJ
authors.lastname: Weaver
authors.forename: M
authors.initials: M
authors.lastname: Dickins
authors.forename: M D
authors.initials: MD
authors.lastname: Burke
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000962:Antimalarials / Q000378:metabolism*; D001189:Aryl Hydrocarbon Hydroxylases; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D005260:Female; D006801:Humans; D006900:Hydroxylation; D007527:Isoenzymes / Q000302:isolation & purification; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D009285:Naphthoquinones / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D000962:Antimalarials; D007527:Isoenzymes; D009285:Naphthoquinones; D003577:Cytochrome P-450 Enzyme System; C045010:BW 58C; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; D039181:Steroid 16-alpha-Hydroxylase