The Podospora anserina lytic polysaccharide monooxygenase PaLPMO9H catalyzes oxidative cleavage of diverse plant cell wall matrix glycans

Abstract

BackgroundThe enzymatic conversion of plant biomass has been recently revolutionized by the discovery of lytic polysaccharide monooxygenases (LPMO) that catalyze oxidative cleavage of polysaccharides. These powerful enzymes are secreted by a large number of fungal saprotrophs and are important components of commercial enzyme cocktails used for industrial biomass conversion. Among the 33 AA9 LPMOs encoded by the genome of Podospora anserina, the PaLPMO9H enzyme catalyzes mixed C1/C4 oxidative cleavage of cellulose and cello-oligosaccharides. Activity of PaLPMO9H on several hemicelluloses has been suggested, but the regioselectivity of the cleavage remained to be determined.ResultsIn this study, we investigated the activity of PaLPMO9H on mixed-linkage glucans, xyloglucan and glucomannan using tandem mass spectrometry and ion mobility–mass spectrometry. Structural analysis of the released products revealed that PaLPMO9H catalyzes C4 oxidative cleavage of mixed-linkage glucans and mixed C1/C4 oxidative cleavage of glucomannan and xyloglucan. Gem-diols and ketones were produced at the non-reducing end, while aldonic acids were produced at the reducing extremity of the products.ConclusionThe ability of PaLPMO9H to target polysaccharides, differing from cellulose by their linkages, glycosidic composition and/or presence of sidechains, could be advantageous for this coprophilous fungus when catabolizing highly variable polysaccharides and for the development of optimized enzyme cocktails in biorefineries.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-017-0749-5) contains supplementary material, which is available to authorized users.

Lytic xylan oxidases from wood-decay fungi unlock biomass degradation

“…These results suggest that AA14 enzymes act on xylans bound to cellulose, which have a rigidity and a conformation similar to that of the underlying cellulose chains 4 . The specific attack of PcAA14 on xylan substrates differentiates this new class of enzymes from all other LPMOs 24,25 , none of which has previously been reported to oxidize xylan in such a selective and efficient manner.…”

Structural and molecular dynamics studies of a C1‐oxidizing lytic polysaccharide monooxygenase from Heterobasidion irregulare reveal amino acids important for substrate recognition

“…For LPMOs that specifically carry out oxidization at the C1 carbon of the pyranose ring (C1‐specific LPMOs), only oxidative cellulolytic activities have been reported . Activities against hemicellulosic substrates have also been reported but have mainly been found in LPMOs able to oxidize at the C4 position, including C4‐specific (oxidize at C4) or C1/C4‐active (oxidize at both C1 and C4) LPMOs .…”

The yeast Geotrichum candidum encodes functional lytic polysaccharide monooxygenases

“…In May 2017, out of 3400 members belonging to the AA9 LPMO family [ 12 ], the 26 characterized ones all originated from filamentous fungi. The substrate specificities of some of these AA9 LPMOs are restricted to cellulose [ 13 ], while others display a broader substrate specificity toward xyloglucans and/or beta-glucans in addition to cellulose [ 14 – 17 ]. A few of them are also active on soluble cello-oligosaccharides [ 15 , 18 , 19 ].…”