Abstract
Myceliophthora thermophyla is a thermophilic industrially relevant fungus that secretes an assortment of hydrolytic and oxidative enzymes for lignocellulose degradation. Among them is glyoxal oxidase (MtGLOx), an extracellular oxidoreductase that oxidizes several aldehydes and α-hydroxy carbonyl substrates coupled to the reduction of O2 to H2O2. This copper metalloprotein belongs to a class of enzymes called radical copper oxidases (CRO) and to the “auxiliary activities” subfamily AA5_1 that is based on the Carbohydrate-Active enZYmes (CAZy) database. Only a few members of this family have been characterized to date. Here, we report the recombinant production, characterization, and structure-function analysis of MtGLOx. Electron Paramagnetic Resonance (EPR) spectroscopy confirmed MtGLOx to be a radical-coupled copper complex and small angle X-ray scattering (SAXS) revealed an extended spatial arrangement of the catalytic and four N-terminal WSC domains. Furthermore, we demonstrate that methylglyoxal and 5-hydroxymethylfurfural (HMF), a fermentation inhibitor, are substrates for the enzyme.
Highlights
Waste plant biomass could be a massive resource for biofuels and commodity chemicals.Two-thirds of a typical biomass is composed of polysaccharides
We report the structural and functional characterization of a multidomain glyoxal oxidase from the thermo tolerant Myceliophthora thermophila M77 and show that 5-hydroxymethylfurfural as a new described substrate for this enzyme, demonstrating its potential in green enzymatic synthesis
Phylogenetic analysis of 47 predicted AA5_1 domains of Glyoxal oxidase (GLOx) enzymes shows that MtGLOx is grouped within a distinct cluster that does not include the characterized GLOx from P. chrysosporium, P
Summary
Waste plant biomass could be a massive resource for biofuels and commodity chemicals.Two-thirds of a typical biomass is composed of polysaccharides. The predominant polysaccharide is cellulose, a β(1,4) glucan followed by hemicelluloses a group of β(1,4) linked polysaccharides that interact with cellulose but can be solubilized in strong alkali [1,2]. Another abundant biomass components is lignin, a polyphenolic complex, which forms an insoluble network that confers rigidity to plant cell walls [3]. Many microorganisms produce a wide variety of hydrolytic enzymes to degrade the polymers These enzymes can be used in some industrial settings to extract sugars from biomass, which can be converted into useful
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