title: Catalytic activities of human debrisoquine 4-hydroxylase cytochrome P450 (CYP2D6) expressed in yeast.
abstract: A 1.57kb BamH1 fragment containing a full-length human debrisoquine 4-hydroxylase cytochrome P450 (CYP2D6) cDNA was inserted into the BglII site of the yeast expression plasmid pMA91 and the resulting recombinant plasmid, PELT1, introduced into Saccharomyces cerevisiae strain AH22. Microsomes prepared from AH22/pELT1 cells gave an absorption maximum at 448 nm and a P450 content of 67 +/- 31 pmol/mg of microsomal protein. No P450 was detectable in microsomes prepared from AH22/pMA91 control cells. A western blot of microsomes prepared from yeast transformed with pELT1 were probed with a monoclonal antibody to CYP2D6 and revealed a strong band with a molecular mass consistent with that of CYP2D6 from human liver microsomes. No corresponding band was observed with microsomes from control yeast transformed with pMA91 alone. Microsomes from AH22/pELT cells showed catalytic activity towards metoprolol (alpha-hydroxylation and O-demethylation, 0.17 and 0.78 nmol/mg protein/h, respectively); and towards sparteine (2- and 5-dehydrogenation, 1.82 and 0.59 nmol/mg protein/h, respectively). The inhibition of metoprolol metabolism by quinidine (Qd) was 200 times more potent than that of quinine (Qn), both for alpha-hydroxylation (Qd IC50 = 0.05 microM; Qn IC50 = 4 microM) and O-demethylation (Qd IC50 = 0.05 microM; Qn IC50 = 4 microM). Negligible metabolism of tolbutamide and S-mephenytoin, substrates of the 2C sub-family, and of p-nitrophenol, a substrate of CYP2E1, was detected, although a trace of the N-deethylated metabolite of lignocaine, thought to be metabolised by CYP3A4, was detected with microsomes from CYP2D6-expressing yeast cells. The results indicate that yeast cells containing human CYP2D6 cDNA express a functionally active form of the enzyme, the immunochemical and catalytic properties of which are consistent with those of human liver.
authors.affiliation: University of Sheffield, Department of Medicine and Pharmacology, Royal Hallamshire Hospital, U.K.
authors.forename: S W
authors.initials: SW
authors.lastname: Ellis
authors.forename: M S
authors.initials: MS
authors.lastname: Ching
authors.forename: P F
authors.initials: PF
authors.lastname: Watson
authors.forename: C J
authors.initials: CJ
authors.lastname: Henderson
authors.forename: A P
authors.initials: AP
authors.lastname: Simula
authors.forename: M S
authors.initials: MS
authors.lastname: Lennard
authors.forename: G T
authors.initials: GT
authors.lastname: Tucker
authors.forename: H F
authors.initials: HF
authors.lastname: Woods
mesh_terms: D019389:Cytochrome P-450 CYP2D6; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000378:metabolism; D006801:Humans; D008790:Metoprolol / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D010957:Plasmids; D011994:Recombinant Proteins / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013034:Sparteine / Q000378:metabolism; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D011994:Recombinant Proteins; D013034:Sparteine; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D019389:Cytochrome P-450 CYP2D6; D008790:Metoprolol