Redox Potential‐Dependent Formation of an Unusual His–Trp Bond in Bilirubin Oxidase

Abstract

Bilirubin oxidase (BOD) belongs to the family of blue multicopper oxidases, and catalyzes the concomitant oxidation of bilirubin to biliverdin and the reduction of molecular oxygen to water via a four-electron reduction system. The active sites of BOD comprise four copper atoms; type I copper (T1Cu) forms a mononuclear site, and a cluster of three copper atoms forms a trinuclear center. In the present study, we determined the high-resolution crystal structures of BOD from the fungus Myrothecium verrucaria. We investigated wild-type (WT) BOD and a BOD mutant called Met467Gln, which is inactive against bilirubin. The structures revealed that a novel post-translational crosslink between Trp396 and His398 is formed in the vicinity of the T1Cu site in WT BOD, whereas it is absent in the Met467Gln mutant. Our structural and computational studies suggest that the His-Trp crosslink adjusts the redox potential of T1Cu to that of bilirubin to efficiently abstract electrons from the substrate.

Redox‐Polymer‐Based High‐Current‐Density Gas‐Diffusion H2‐Oxidation Bioanode Using [FeFe] Hydrogenase from Desulfovibrio desulfuricans in a Membrane‐free Biofuel Cell

“… a) Scheme of the proposed multilayer gas diffusion electrode modified with the DdHydAB (1HFE) hydrogenase wired through the viologen‐modified polymers P(GMA‐BA‐PEGMA)‐vio and P(N 3 MA‐BA‐GMA)‐vio. b) Schematic of the dual gas diffusion membrane‐free H 2 /O 2 powered biofuel cell equipped with the bioanode depicted in (a) and an O 2 ‐reducing bilirubin oxidase (6IQZ) based biocathode operated in a direct electron transfer regime. Not drawn to scale.…”

Inhibition in multicopper oxidases: a critical review

“…144,145 Akter et al identified a covalent bond between a surface tryptophan and one of the histidine residues coordinating the T1 Cu, and proposed that it raises the redox potential of the T1 site to match that of the bilirubin substrate. 146 In a "yellow" laccase from Sclerotinia sclerotiorum, Mot et al identified a surface tyrosine residue at the T1 site, which forms a reversible adduct with the electron-donor substrate. 124 The surface residues near the T1 site also influence the dipole moment of MCOs.…”

Eine Redoxpolymer‐basierte Gasdiffusions‐H2‐Oxidationsbioanode mit hoher Stromdichte unter Verwendung von [FeFe]‐Hydrogenase aus Desulfovibrio desulfuricans integriert in einer membranfreien Biobrennstoffzelle

“… a) Schema der vorgeschlagenen Mehrschicht‐Gasdiffusionselektrode, modifiziert mit der DdHydAB (1HFE [28] )‐Hydrogenase, die durch die Viologen‐modifizierten Polymere P(GMA‐BA‐PEGMA)‐vio und P(N 3 MA‐BA‐GMA)‐vio kontaktiert wird. b) Schema der auf zwei Gasdiffusionselektroden basierenden membranfreien H 2 /O 2 ‐Biobrennstoffzelle, ausgestattet mit der in (a) dargestellten Bioanode und einer auf der O 2 reduzierenden Bilirubinoxidase (6IQZ) basierenden Biokathode, die in einem direkten Elektronentransfer‐Regime betrieben wird. Nicht maßstabsgetreu gezeichnet.…”