Allelic variants of human cytochrome P450 2C9: baculovirus-mediated expression, purification, structural characterization, substrate stereoselectivity, and prochiral selectivity of the wild-type and I359L mutant forms.

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Haining RL, Hunter AP, Veronese ME, Trager WF, Rettie AE

Arch Biochem Biophys. 1996 Sep 15;333(2):447-58.

PubMed ID

8809086 [ View in PubMed

]

Abstract

The purpose of the present studies was to define the role of the I359L allelic variant of CYP2C9 in the metabolism of the low therapeutic index anticoagulant warfarin, by performing in vitro kinetic studies with the two enantiomers of the drug. To obtain sufficient quantities of these variants to perform kinetic studies at physiologically relevant substrate concentrations, methodology was established for the high-level expression, purification, and structural characterization of wild-type CYP2C9 and CYP2C9V1 using the baculovirus system. Both forms were expressed at levels up to 250 nmol/liter and purified in 50-55% yield to specific contents of 13-14 nmol holoenzyme/mg protein. The purified preparations were characterized by Edman degradation and electrospray-mass spectrometry. Both forms of the enzyme metabolized the pharmacologically more potent (S)-enantiomer of warfarin with the same regioselectivity; however, CYP2C9V1 exhibited a fivefold lower Vmax and a fivefold higher Km compared to the wild-type enzyme for this substrate. Neither form of the enzyme formed significant quantities of the (R)-warfarin phenols. Additional studies performed with prochiral arylalkyl sulfides provided confirmation of the low turnover rates catalyzed by CYP2C9V1 and demonstrated further that sulfoxide product stereochemistry did not differ significantly between the two variants. Therefore, decreased catalytic efficiency rather than a gross alteration in substrate orientation appears to be the consequence of this putative active-site mutation. The greatly decreased catalytic efficiency of the I359L variant suggests that leucine homozygotes would eliminate (S)-warfarin, and probably many other CYP2C9 substrates, at much slower rates in vivo than individuals expressing the wild-type enzyme.

DrugBank Data that Cites this Article

Polypeptides

Name	UniProt ID
Cytochrome P450 2C9	P11712	Details

Pharmaco-genomics

Drug	Interacting Gene/Enzyme	Allele name	Genotypes	Defining change(s)	Type(s)	Description	Details
Warfarin	Cytochrome P450 2C9 Gene symbol: CYP2C9 UniProt: P11712	CYP2C9*3	Not Available	1075A>C (rs1057910)	Effect Inferred	Poor drug metabolizer, lower dose requirements	Details
Phenprocoumon	Cytochrome P450 2C9 Gene symbol: CYP2C9 UniProt: P11712	CYP2C9*3	Not Available	1075A>C (rs1057910)	ADR Inferred	Associated with delayed stabilization. If carrier of rs9934438 as well, increased risk of severe overanticoagulation.	Details