Stereoselective hexobarbital 3'-hydroxylation by CYP2C19 expressed in yeast cells and the roles of amino acid residues at positions 300 and 476.
We examined the enzymatic function of recombinant CYP2C19 in enantiomeric hexobarbital (HB) 3'-hydroxylation, and searched the roles of amino acid residues, such as Phe-100, Phe-114, Asp-293, Glu-300, and Phe-476 of CYP2C19 in the stereoselective HB 3'-hydroxylation, using a yeast cell expression system and site-directed mutagenesis method. CYP2C19 wild-type exerted substrate enantioselectivity of (R)-HB>>(S)-HB and metabolite diastereoselectivity of 3'(R)<3'(S) in 3'-hydroxylation of HB enantiomers. The substitution of Asp-293 by alanine failed to yield an observable peak at 450 nm in its reduced carbon monoxide-difference spectrum. CYP2C19-E300A and CYP2C19-E300V with alanine and valine, respectively, in place of Glu-300 exerted total HB 3'-hydroxylation activities of 45 and 108%, respectively, that of the wild-type. Interestingly, these two mutants showed substrate enantioselectivity of (R)-HB<(S)-HB, which is opposite to that of the wild-type, while metabolite diasteroselectivity remained unchanged. The replacement of Phe-476 by alanine increased total HB 3'-hydroxylation activity to approximately 3-fold that of the wild-type. Particularly, 3'(S)-OH-(S)-HB-forming activity elevated to 7-fold that of the wild-type, resulting in the reversal of the substrate enantioselectivity. In contrast, the substitution of phenylalanine at positions 100 and 114 by alanine did not produce a remarkable change in the total activity or the substrate enantioselectivity. These results indicate that Glu-300 and Phe-476 are important in stereoselective oxidation of HB enantiomers by CYP2C19.
Saito
Keita
K
Laboratory of Health Chemistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Dan
Hikari
H
Masuda
Kazufumi
K
Katsu
Takashi
T
Hanioka
Nobumitsu
N
Yamamoto
Shigeo
S
Miyano
Kazuko
K
Yamano
Shigeru
S
Narimatsu
Shizuo
S
D019943:Amino Acid Substitution; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D020134:Catalytic Domain / Q000235:genetics; D065731:Cytochrome P-450 CYP2C19; D017931:DNA Primers / Q000235:genetics; D006591:Hexobarbital / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D010957:Plasmids / Q000235:genetics; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D013237:Stereoisomerism; D013379:Substrate Specificity
D017931:DNA Primers; D011994:Recombinant Proteins; D006591:Hexobarbital; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19