title: Electron-transfer rates govern product distribution in electrochemically-driven P450-catalyzed dioxygen reduction.
abstract: Developing electrode-driven biocatalytic systems utilizing the P450 cytochromes for selective oxidations depends not only on achieving electron transfer (ET) but also doing so at rates that favor native-like turnover. Herein we report studies that correlate rates of heme reduction with ET pathways and resulting product distributions. We utilized single-surface cysteine mutants of the heme domain of P450 from Bacillus megaterium and modified the thiols with N-(1-pyrene)-iodoacetamide, affording proteins that could bond to basal-plane graphite. Of the proteins examined, Cys mutants at position 62, 383, and 387 were able to form electroactive monolayers with similar E(1/2) values (-335 to -340mV vs AgCl/Ag). Respective ET rates (k(s)(o)) and heme-cysteine distances for 62, 383, and 387 are 50 s(-1) and 16Ǻ, 0.8 s(-1) and 25Ǻ, and 650 s(-1) and 19Ǻ. Experiments utilizing rotated-disk electrodes were conducted to determine the products of P450-catalyzed dioxygen reduction. We found good agreement between ET rates and product distributions for the various mutants, with larger k(s)(o) values correlating with more electrons transferred per dioxygen during catalysis.
authors.affiliation: Occidental College, Department of Chemistry, Los Angeles, CA 90041, United States.
authors.forename: Clairisse
authors.initials: C
authors.lastname: van der Felt
authors.forename: Kevork
authors.initials: K
authors.lastname: Hindoyan
authors.forename: Kang
authors.initials: K
authors.lastname: Choi
authors.forename: Nazafarin
authors.initials: N
authors.lastname: Javdan
authors.forename: Peter
authors.initials: P
authors.lastname: Goldman
authors.forename: Rose
authors.initials: R
authors.lastname: Bustos
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Star
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Hunter
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hill
authors.forename: Aram
authors.initials: A
authors.lastname: Nersissian
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Udit
mesh_terms: D001410:Bacillus megaterium / Q000201:enzymology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004563:Electrochemistry / Q000379:methods*; D004579:Electron Transport / Q000502:physiology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*
chemical_list: D003577:Cytochrome P-450 Enzyme System; D010100:Oxygen