Detection and Characterization of a Novel Copper-Dependent Intermediate in a Lytic Polysaccharide Monooxygenase.
Chemistry
; 26(2): 454-463, 2020 Jan 07.
Article
en En
| MEDLINE
| ID: mdl-31603264
ABSTRACT
Lytic polysaccharide monooxygenases (LPMOs) are copper-containing enzymes capable of oxidizing crystalline cellulose which have large practical application in the process of refining biomass. The catalytic mechanism of LPMOs still remains debated despite several proposed reaction mechanisms. Here, we report a long-lived intermediate (t1/2 =6-8 minutes) observed in an LPMO from Thermoascus aurantiacus (TaLPMO9A). The intermediate with a strong absorption around 420â
nm is formed when reduced LPMO-CuI reacts with sub-equimolar amounts of H2 O2 . UV/Vis absorption spectroscopy, electron paramagnetic resonance, resonance Raman and stopped-flow spectroscopy suggest that the observed long-lived intermediate involves the copper center and a nearby tyrosine (Tyr175). Additionally, activity assays in the presence of sub-equimolar amounts of H2 O2 showed an increase in the LPMO oxidation of phosphoric acid swollen cellulose. Accordingly, this suggests that the long-lived copper-dependent intermediate could be part of the catalytic mechanism for LPMOs. The observed intermediate offers a new perspective into the oxidative reaction mechanism of TaLPMO9A and hence for the biomass oxidation and the reactivity of copper in biological systems.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Cobre
/
Oxigenasas de Función Mixta
Tipo de estudio:
Diagnostic_studies
Idioma:
En
Revista:
Chemistry
Asunto de la revista:
QUIMICA
Año:
2020
Tipo del documento:
Article
País de afiliación:
Dinamarca