Abstract
Lytic polysaccharide monooxygenases (LPMOs) are key enzymes in both the natural carbon cycle and the biorefinery industry. Understanding the molecular basis of LPMOs acting on polysaccharide substrates is helpful for improving industrial cellulase cocktails. Here we analyzed the sequences, structures, and substrate binding modes of LPMOs to uncover the factors that influence substrate specificity and regioselectivity. Our results showed that the different compositions of a motif located on L2 affect the electrostatic potentials of substrate binding surfaces, which in turn affect substrate specificities of AA10 LPMOs. A conserved Asn at a distance of 7 Å from the active center Cu might, together with the conserved Ser immediately before the second catalytic His, determine the localization of LPMOs on substrate, and thus contribute to C4-oxidizing regioselectivity. The findings in this work provide an insight into the molecular basis of substrate specificity and regioselectivity of LPMOs.
Highlights
Lytic polysaccharide monooxygenases (LPMOs) are a group of copper-dependent enzymes that catalyze the oxidatively cleavage of glycoside bonds in polysaccharides, such as cellulose and chitin [1,2]
AA10 LPMOs have diverse substrate specificities, some of which act on chitin, while others act on cellulose
To study the factors affecting substrate specificity, we first analyzed the sequences of catalytic domain of characterized AA10 LPMOs
Summary
Lytic polysaccharide monooxygenases (LPMOs) are a group of copper-dependent enzymes that catalyze the oxidatively cleavage of glycoside bonds in polysaccharides, such as cellulose and chitin [1,2]. The ability of these enzymes to boost the degradation of crystalline polysaccharides represents a promising resource for development of industrial enzyme cocktails for biomass processing [3,4]. Members of AA9 are cellulose-active LPMOs from fungi, with C1- and/or C4-oxidizing activity [7]. There is no cellulose-active LPMOs oxidizing C4 carbon only found in AA10 family [8]. AA16 are fungal LPMOs with cellulose-activity [6]
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