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Crystal Structure of Human Microsomal P450 3A4
Structural highlights
FunctionCP3A4_HUMAN Cytochromes P450 are a group of heme-thiolate monooxygenases. In liver microsomes, this enzyme is involved in an NADPH-dependent electron transport pathway. It performs a variety of oxidation reactions (e.g. caffeine 8-oxidation, omeprazole sulphoxidation, midazolam 1'-hydroxylation and midazolam 4-hydroxylation) of structurally unrelated compounds, including steroids, fatty acids, and xenobiotics. Acts as a 1,8-cineole 2-exo-monooxygenase. The enzyme also hydroxylates etoposide.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe structure of P450 3A4 was determined by x-ray crystallography to 2.05-A resolution. P450 3A4 catalyzes the metabolic clearance of a large number of clinically used drugs, and a number of adverse drug-drug interactions reflect the inhibition or induction of the enzyme. P450 3A4 exhibits a relatively large substrate-binding cavity that is consistent with its capacity to oxidize bulky substrates such as cyclosporin, statins, taxanes, and macrolide antibiotics. Family 3A P450s also exhibit unusual kinetic characteristics that suggest simultaneous occupancy by smaller substrates. Although the active site volume is similar to that of P450 2C8 (PDB code: 1PQ2), the shape of the active site cavity differs considerably due to differences in the folding and packing of portions of the protein that form the cavity. Compared with P450 2C8, the active site cavity of 3A4 is much larger near the heme iron. The lower constraints on the motions of small substrates near the site of oxygen activation may diminish the efficiency of substrate oxidation, which may, in turn, be improved by space restrictions imposed by the presence of a second substrate molecule. The structure of P450 3A4 should facilitate a better understanding of the substrate selectivity of the enzyme. The structure of human microsomal cytochrome P450 3A4 determined by X-ray crystallography to 2.05-A resolution.,Yano JK, Wester MR, Schoch GA, Griffin KJ, Stout CD, Johnson EF J Biol Chem. 2004 Sep 10;279(37):38091-4. Epub 2004 Jul 16. PMID:15258162[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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