Cytochrome b5 enhances androgen synthesis by rapidly reducing the CYP17A1 oxy-complex in the lyase step

Ruchia Duggal, Ilia G. Denisov, Stephen Sligar

Research output: Contribution to journalLetter

Abstract

Cytochrome P450 17A1 (CYP17A1) catalyzes the synthesis of androgens from the steroid precursors pregnenolone and progesterone in a two-step reaction process: allylic hydroxylation and carbo-carbon bond scission. Cytochrome b5 (Cyt-b5) is a stimulator of the second lyase reaction, but the chemical mechanism is unclear. We have shown previously that this stimulatory effect requires redox active Cyt-b5. To investigate the origin of the lyase reaction enhancement by electron transfer from Cyt-b5, we measured the reduction rates of oxy-ferrous substrate-bound CYP17A1 by Cyt-b5 and by cytochrome P450 reductase (CPR) coincorporated in Nanodiscs using stopped flow spectroscopy. We observed that Cyt-b5 reduces oxy-ferrous CYP17A1 10-fold faster than CPR, with the rate similar to that observed in a ternary complex of all three proteins.

Original languageEnglish (US)
Pages (from-to)2282-2288
Number of pages7
JournalFEBS Letters
Volume592
Issue number13
DOIs
StatePublished - Jul 1 2018

Fingerprint

Cytochromes b5
Lyases
Cytochrome P-450 Enzyme System
Androgens
NADPH-Ferrihemoprotein Reductase
Pregnenolone
Hydroxylation
Charcoal
Oxidation-Reduction
Progesterone
Spectrum Analysis
Carbon
Steroids
Spectroscopy
Electrons
Substrates
Proteins

Keywords

  • Nanodisc
  • androgen biosynthesis
  • cytochrome P450
  • cytochrome b5

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

Cytochrome b5 enhances androgen synthesis by rapidly reducing the CYP17A1 oxy-complex in the lyase step. / Duggal, Ruchia; Denisov, Ilia G.; Sligar, Stephen.

In: FEBS Letters, Vol. 592, No. 13, 01.07.2018, p. 2282-2288.

Research output: Contribution to journalLetter

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AU - Sligar, Stephen

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N2 - Cytochrome P450 17A1 (CYP17A1) catalyzes the synthesis of androgens from the steroid precursors pregnenolone and progesterone in a two-step reaction process: allylic hydroxylation and carbo-carbon bond scission. Cytochrome b5 (Cyt-b5) is a stimulator of the second lyase reaction, but the chemical mechanism is unclear. We have shown previously that this stimulatory effect requires redox active Cyt-b5. To investigate the origin of the lyase reaction enhancement by electron transfer from Cyt-b5, we measured the reduction rates of oxy-ferrous substrate-bound CYP17A1 by Cyt-b5 and by cytochrome P450 reductase (CPR) coincorporated in Nanodiscs using stopped flow spectroscopy. We observed that Cyt-b5 reduces oxy-ferrous CYP17A1 10-fold faster than CPR, with the rate similar to that observed in a ternary complex of all three proteins.

AB - Cytochrome P450 17A1 (CYP17A1) catalyzes the synthesis of androgens from the steroid precursors pregnenolone and progesterone in a two-step reaction process: allylic hydroxylation and carbo-carbon bond scission. Cytochrome b5 (Cyt-b5) is a stimulator of the second lyase reaction, but the chemical mechanism is unclear. We have shown previously that this stimulatory effect requires redox active Cyt-b5. To investigate the origin of the lyase reaction enhancement by electron transfer from Cyt-b5, we measured the reduction rates of oxy-ferrous substrate-bound CYP17A1 by Cyt-b5 and by cytochrome P450 reductase (CPR) coincorporated in Nanodiscs using stopped flow spectroscopy. We observed that Cyt-b5 reduces oxy-ferrous CYP17A1 10-fold faster than CPR, with the rate similar to that observed in a ternary complex of all three proteins.

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