Resonance Raman Spectroscopy Reveals that Substrate Structure Selectively Impacts the Heme-Bound Diatomic Ligands of CYP17

Authors

Piotr J. Mak, Marquette UniversityFollow
Michael C. Gregory, University of Illinois at Urbana-Champaign
Stephen G. Sligar, University of Illinois at Urbana-Champaign
James R. Kincaid, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

11 p.

Publication Date

1-14-2014

Publisher

American Chemical Society

Source Publication

Biochemistry

Source ISSN

0006-2960

Original Item ID

DOI: 10.1021/bi4014424

Abstract

An important function of steroidogenic cytochromes P450 is the transformation of cholesterol to produce androgens, estrogens, and the corticosteroids. The activities of cytochrome P450c17 (CYP17) are essential in sex hormone biosynthesis, with severe developmental defects being a consequence of deficiency or mutations. The first reaction catalyzed by this multifunctional P450 is the 17α-hydroxylation of pregnenolone (PREG) to 17α-hydroxypregnenolone (17-OH PREG) and progesterone (PROG) to 17α-hydroxyprogesterone (17-OH PROG). The hydroxylated products then either are used for production of corticoids or undergo a second CYP17 catalyzed transformation, representing the first committed step of androgen formation. While the hydroxylation reactions are catalyzed by the well-known Compound I intermediate, the lyase reaction is believed to involve nucleophilic attack of the earlier peroxo- intermediate on the C20-carbonyl. Herein, resonance Raman (rR) spectroscopy reveals that substrate structure does not impact heme structure for this set of physiologically important substrates. On the other hand, rR spectra obtained here for the ferrous CO adducts with these four substrates show that substrates do interact differently with the Fe-C-O fragment, with large differences between the spectra obtained for the samples containing 17-OH PROG and 17-OH PREG, the latter providing evidence for the presence of two Fe-C-O conformers. Collectively, these results demonstrate that individual substrates can differentially impact the disposition of a heme-bound ligand, including dioxygen, altering the reactivity patterns in such a way as to promote preferred chemical conversions, thereby avoiding the profound functional consequences of unwanted side reactions.

Comments

Accepted version. Biochemistry, Vol. 53, No. 1 (January 14, 2014): 90-100. DOI. © 2013 American Chemical Society. Used with permission.

Recommended Citation

Mak, Piotr J.; Gregory, Michael C.; Sligar, Stephen G.; and Kincaid, James R., "Resonance Raman Spectroscopy Reveals that Substrate Structure Selectively Impacts the Heme-Bound Diatomic Ligands of CYP17" (2014). Chemistry Faculty Research and Publications. 379.
https://epublications.marquette.edu/chem_fac/379