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Publication Abstract from PubMed

CYP51 enzymes (sterol 14alpha-demethylases) are cytochromes P450 that catalyze multistep reactions. The CYP51 reaction occurs in all biological kingdoms and is essential in sterol biosynthesis. It removes the 14alpha-methyl group from cyclized sterol precursors by first forming an alcohol, then an aldehyde, and finally eliminating formic acid with the introduction of a Delta14-15 double bond in the sterol core. The first two steps are typical hydroxylations, mediated by an electrophilic Compound I mechanism. The third step, C-C bond cleavage, has been proposed to involve either Compound I (i.e. FeO3+) or, alternatively, a proton transfer-independent nucleophilic ferric peroxo anion (Compound 0, i.e. Fe3+O2-). Here, using comparative crystallographic and biochemical analyses of wild type human CYP51 (CYP51A1) and its D231A/H314A mutant, whose proton delivery network is destroyed (as evidenced in a 1.98 A X-ray structure in complex with lanosterol), we demonstrate that deformylation of the 14alpha-carboxaldehyde intermediate requires an active proton relay network to drive the catalysis. These results indicate a unified, Compound I-based mechanism for all three steps of the CYP51 reaction, as previously established for CYP11A1 and CYP19A1. We anticipate that our approach can be applied for mechanistic studies of other P450s that catalyze multistep reactions such as C-C bond cleavage.

A requirement for an active proton delivery network supports a Compound I mediated C-C bond cleavage in CYP51 catalysis.,Hargrove TY, Wawrzak Z, Guengerich FP, Lepesheva GI J Biol Chem. 2020 Jun 3. pii: RA120.014064. doi: 10.1074/jbc.RA120.014064. PMID:32493730^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.