A family of AA9 lytic polysaccharide monooxygenases in Aspergillus nidulans is differentially regulated by multiple substrates and at least one is active on cellulose and xyloglucan

Abstract

Fungal genomes contain multiple genes encoding AA9 lytic polysaccharide monooxygenases (LPMOs), a recently discovered class of enzymes known to be active on cellulose and expressed when grown on biomass. Because of extensive genetic and biochemical data already available, Aspergillus nidulans offers an excellent model system to study the need for multiple AA9 LPMOs and their activity during oxidative degradation of biomass. We provide the first report on regulation of the entire family of AA9 LPMOs in A. nidulans over a range of polysaccharides including xylan, xyloglucan, pectin, glucan, and cellulose. We have successfully cloned and expressed AN3046, an AA9 LPMO in A. nidulans that is active on cellulose. Additionally, we performed mass spectral analyses that show the enzyme is active on the hemicellulose xyloglucan. The AN3046 LPMO showed synergy with other hydrolases in degrading sorghum stover. Our data showing activity of the overexpressed LPMO on cellulose and xyloglucan provides further evidence for the breadth of substrates acted on by AA9 LPMOs.

Keywords: A. nidulans; AA9 LPMO; Biomass degradation; Cellulose; Lytic polysaccharide monooxygenases; Oxidative cleavage; Pectin; Transcriptional regulation; Xyloglucan.