Cytochrome P450 3A is the main enzyme subfamily involved in the metabolism of a variety of marketed medicines. It is generally believed that the substrate specificity of polymorphic P450 3A5 is similar to that of the predominant P450 3A4 isoform, although some differences in catalytic properties have been found. In liver microsomes, this enzyme is involved in an NADPH-dependent electron transport pathway. It oxidizes a variety of structurally unrelated compounds, including steroids, fatty acids, and xenobiotics.
The 5′-terminus of a P450 3A5 cDNA was modified for optimal expression in Escherichia coli using the vector pCW, by aligning the MALLLAVFL N-terminal sequence of recombinant bovine P450 17A (H. J. Barnes, M. P. Arlotto, and M. R. Waterman, (1991) Proc. Natl. Acad. Sci. USA 88, 5597-5601) to the 3A5 cDNA. Cytochromes P450 are a group of heme-thiolate monooxygenases.
Purified P450 3A5 was active in nifedipine oxidation, testosterone 6β-hydroxylation, aflatoxin 3α-hydroxylation and 8,9-epoxidation, N-ethylmorphine N-demethylation, erythromycin N-demethylation, and d-benzphetamine N-demethylation. Enhanced midazolam hydroxylation and cyclosporin metabolism occur in an in vitro P450 3A5 system and in liver microsomes expressing P450 3A5 in the presence of thalidomide. The reconstitution of nifedipine oxidation, testosterone 6β-hydroxylation, and the aflatoxin oxidation activities showed dependence upon the presence of cytochrome b5, divalent cations, phospholipid mixtures, glutathione, and cholate similar to that previously found for purified P450 3A4.
Synonyms: CYP3A5 HR
Stability: 2 months
Storage: -80°C
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