RT Journal Article
SR Electronic
T1 Detection and characterization of a novel copper-dependent intermediate in a lytic polysaccharide monooxygenase
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 610865
DO 10.1101/610865
A1 Raushan K. Singh
A1 Bart v. Oort
A1 Benedikt Möllers
A1 David A. Russo
A1 Ranjitha Singh
A1 Høgni Weihe
A1 Manish K. Tiwari
A1 Roberta Croce
A1 Paul E. Jensen
A1 Claus Felby
A1 Morten J. Bjerrum
YR 2019
UL http://biorxiv.org/content/early/2019/04/17/610865.abstract
AB Lytic polysaccharide monooxygenases (LPMOs) are copper-containing enzymes capable of oxidizing crystalline cellulose and the enzyme has large practical application in the process of refining biomass. The LPMO catalytic mechanism still remains debated despite several proposed reaction mechanisms. Here, we report a long-lived intermediate (t½ = 6 – 8 minutes) observed in an LPMO from Thermoascus aurantiacus (TaLPMO9A). The intermediate with a strong absorption around 420 nm is formed when reduced LPMO-Cu(I) reacts with H2O2. UV-vis absorption spectroscopy, electron paramagnetic resonance (EPR), and stopped-flow spectroscopy indicate that the observed long-lived intermediate involves the copper center and a nearby tyrosine (Tyr175). We propose that the reaction with H2O2 first forms a highly reactive short-lived Cu(III)-intermediate which is subsequently transformed into the observed long-lived copper-dependent intermediate. Since sub-equimolar amount of H2O2 to LPMO boosts oxidation of phosphoric acid swollen cellulose (PASC) suggests that the long-lived copper-dependent intermediate is part of the catalytic mechanism for LPMOs. The proposed mechanism offers new perspectives in the oxidative reaction mechanism of copper enzymes and hence for the biomass oxidation and the reactivity of copper in biological systems.