Serial femtosecond crystallography reveals the role of water in the one- or two-electron redox chemistry of compound I in the catalytic cycle of the B-type dye-decolorizing peroxidase DtpB

DOI: 10.1021/acscatal.2c03754

Authors: Marina Lucic (University of Essex) , Matthew T. Wilson (University of Essex) , Takehiko Tosha (RIKEN, Spring-8 Center) , Hiroshi Sugimoto (RIKEN, Spring-8 Center) , Anastasiia Shilova (Diamond Light Source) , Danny Axford (Diamond Light Source) , Robin L. Owen (Diamond Light Source) , Michael A. Hough (University of Essex; Diamond Light Source) , Jonathan A. R. Worrall (University of Essex)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Catalysis , VOL 26 , PAGES 13349 - 13359

State: Published (Approved)
Published: October 2022
Diamond Proposal Number(s): 25108 , 28583

Abstract: Controlling the reactivity of high-valent Fe(IV)–O catalytic intermediates, Compounds I and II, generated in heme enzymes upon reaction with dioxygen or hydrogen peroxide, is important for function. It has been hypothesized that the presence (wet) or absence (dry) of distal heme pocket water molecules can influence whether Compound I undergoes sequential one-electron additions or a concerted two-electron reduction. To test this hypothesis, we investigate the role of water in the heme distal pocket of a dye-decolorizing peroxidase utilizing a combination of serial femtosecond crystallography and rapid kinetic studies. In a dry distal heme site, Compound I reduction proceeds through a mechanism in which Compound II concentration is low. This reaction shows a strong deuterium isotope effect, indicating that reduction is coupled to proton uptake. The resulting protonated Compound II (Fe(IV)–OH) rapidly reduces to the ferric state, giving the appearance of a two-electron transfer process. In a wet site, reduction of Compound I is faster, has no deuterium effect, and yields highly populated Compound II, which is subsequently reduced to the ferric form. This work provides a definitive experimental test of the hypothesis advanced in the literature that relates sequential or concerted electron transfer to Compound I in wet or dry distal heme sites.

Journal Keywords: heme proteins; Compounds I and II; serial femtosecond X-ray crystallography; solvent kinetic isotope effect; water; kinetics

Diamond Keywords: Enzymes

Subject Areas: Chemistry, Biology and Bio-materials

Diamond Offline Facilities: XFEL-Hub
Instruments: I24-Microfocus Macromolecular Crystallography

Other Facilities: BL2 EH3 at SACLA

Added On: 24/10/2022 08:50

Documents:
acscatal.2c03754.pdf

Discipline Tags:

Biochemistry Catalysis Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)