Faculty Collaboration Database

Resonance Raman spectroscopy reveals that substrate structure selectively impacts the heme-bound diatomic ligands of CYP17. Biochemistry 2014 Jan 14;53(1):90-100

Date

12/18/2013

Pubmed ID

24328388

Pubmed Central ID

PMC3922198

DOI

10.1021/bi4014424

Scopus ID

2-s2.0-84892591956 (requires institutional sign-in at Scopus site)   21 Citations

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.

Author List

Mak PJ, Gregory MC, Sligar SG, Kincaid JR

Author

James Kincaid PhD Department Chair and Professor, Biophysical Chemistry in the Chemistry department at Marquette University

MESH terms used to index this publication - Major topics in bold

Catalytic Domain
Heme
Humans
Hydroxylation
Ligands
Pregnenolone
Progesterone
Spectrum Analysis, Raman
Steroid 17-alpha-Hydroxylase
Substrate Specificity