Fluconazole binding and sterol demethylation in three CYP51 isoforms indicate differences in active site topology.

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Bellamine A, Lepesheva GI, Waterman MR

Fluconazole binding and sterol demethylation in three CYP51 isoforms indicate differences in active site topology.

J Lipid Res. 2004 Nov;45(11):2000-7. Epub 2004 Aug 16.

PubMed ID

15314102 [ View in PubMed

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Abstract

14alpha-Demethylase (CYP51) is a key enzyme in all sterol biosynthetic pathways (animals, fungi, plants, protists, and some bacteria), catalyzing the removal of the C-14 methyl group following cyclization of squalene. Based on mutations found in CYP51 genes from Candida albicans azole-resistant isolates obtained after fluconazole treatment of fungal infections, and using site-directed mutagenesis, we have found that fluconazole binding and substrate metabolism vary among three different CYP51 isoforms: human, fungal, and mycobacterial. In C. albicans, the Y132H mutant from isolates shows no effect on fluconazole binding, whereas the F145L mutant results in a 5-fold increase in its IC(50) for fluconazole, suggesting that F145 (conserved only in fungal 14alpha-demethylases) interacts with this azole. In C. albicans, F145L accounts, in part, for the difference in fluconazole sensitivity reported between mammals and fungi, providing a basis for treatment of fungal infections. The C. albicans Y132H and human Y145H CYP51 mutants show essentially no effect on substrate metabolism, but the Mycobacterium tuberculosis F89H CYP51 mutant loses both its substrate binding and metabolism. Because these three residues align in the three isoforms, the results indicate that their active sites contain important structural differences, and further emphasize that fluconazole and substrate binding are uncoupled properties.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Fluconazole	Cytochrome P450 51	Protein	Yeast	Yes	Inhibitor	Details
Tioconazole	Cytochrome P450 51	Protein	Yeast	Yes	Antagonist	Details