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Publication Abstract from PubMed

Cytochrome P450 (P450) 17A1 catalyzes the oxidations of progesterone and pregnenolone and is the major source of androgens. The enzyme catalyzes both 17alpha-hydroxylation and a subsequent 17alpha, 20-lyase reaction, and several mechanisms have been proposed for the latter step. Zebrafish P450 17A2 catalyzes only the 17alpha-hydroxylations. We previously reported high similarity of the crystal structures of zebrafish P450 17A1 and 17A2 and human P450 17A1 (Pallan et al. (2015) J. Biol. Chem. 290, 3248- 3268). Five residues near the heme, which differed, were changed. We also crystallized this five-residue zebrafish P450 17A1 mutant, and the active site still resembled the structure in the other proteins, with some important differences. These P450 17A1 and 17A2 mutants had catalytic profiles more similar to each other than did the wild-type proteins. Docking with these structures can explain several minor products, which require multiple enzyme conformations. The 17alpha-hydroperoxy (OOH) derivatives of the steroids were used as oxygen surrogates. Human P450 17A1 and zebrafish P450s 17A1 and P450 17A2 readily converted these to the lyase products in the absence of other proteins or cofactors (with catalytically competent kinetics), plus hydroxylated 17alpha-hydroxy steroids. The 17alpha-OOH results indicate that a "Compound I" (FeO(3+)) intermediate is capable of formation and can be used to rationalize the products. We conclude that zebrafish P450 17A2 is capable of lyase activity with the 17alpha-OOH steroids because it can achieve an appropriate conformation for lyase catalysis in this system that is precluded in the conventional reaction.

Inherent steroid 17alpha,20-lyase activity in defunct cytochrome P450 17A enzymes.,Gonzalez E, Johnson KM, Pallan PS, Phan TTN, Zhang W, Lei LI, Wawrzak Z, Yoshimoto FK, Egli M, Guengerich FP J Biol Chem. 2017 Dec 6. pii: RA117.000504. doi: 10.1074/jbc.RA117.000504. PMID:29212707^[1]

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