7p3u
Chitin-active fungal AA11 LPMO
Structural highlights
FunctionLP11A_ASPFC Lytic polysaccharide monooxygenase (LPMO) that depolymerizes chitin via the oxidation of scissile beta-(1-4)-glycosidic bonds, yielding C1 or C4 oxidation products (PubMed:34798071). Catalysis by LPMOs requires the reduction of the active-site copper from Cu(II) to Cu(I) by a reducing agent and H(2)O(2) or O(2) as a cosubstrate (PubMed:34798071). Has considerable affinity for alpha-chitin and, more so, beta-chitin (PubMed:34798071). Active toward both alpha-chitin and beta-chitin allomorphs and enhances chitin degradation by an endoacting chitinase, in particular for alpha-chitin, and so plays a role in fungal chitin turnover (PubMed:34798071). The catalytic activity increases when supplying reactions with hydrogen peroxide, confirming that it has peroxygenase activity (PubMed:34798071). Does not show activity on phosphoric acid-swollen cellulose (PASC), Avicel, tamarind xyloglucan, birchwood xylan, beechwood xylan, acetyl glucuronoxylan from aspen, ivory nut mannan, acetylated konjac glucomannan, potato starch, heparin, hyaluronic acid, and chitosan (PubMed:34798071).[1] Publication Abstract from PubMedThe discovery of oxidative cleavage of recalcitrant polysaccharides by lytic polysaccharide monooxygenases (LPMOs) has affected the study and industrial application of enzymatic biomass processing. Despite being widespread in fungi, LPMOs belonging to the auxiliary activity (AA) family AA11 have been understudied. While these LPMOs are considered chitin active, some family members have little or no activity toward chitin, and the only available crystal structure of an AA11 LPMO lacks features found in bacterial chitin-active AA10 LPMOs. Here, we report structural and functional characteristics of a single-domain AA11 LPMO from Aspergillus fumigatus, AfAA11A. The crystal structure shows a substrate-binding surface with features resembling those of known chitin-active LPMOs. Indeed, despite the absence of a carbohydrate-binding module, AfAA11A has considerable affinity for alpha-chitin and, more so, beta-chitin. AfAA11A is active toward both these chitin allomorphs and enhances chitin degradation by an endoacting chitinase, in particular for alpha-chitin. The catalytic activity of AfAA11A on chitin increases when supplying reactions with hydrogen peroxide, showing that, like LPMOs from other families, AfAA11A has peroxygenase activity. These results show that, in stark contrast to the previously characterized AfAA11B from the same organism, AfAA11A likely plays a role in fungal chitin turnover. Thus, members of the hitherto rather enigmatic family of AA11 LPMOs show considerable structural and functional differences and may have multiple roles in fungal physiology. Characterization of a lytic polysaccharide monooxygenase from Aspergillus fumigatus shows functional variation among family AA11 fungal LPMOs.,Stopamo FG, Rohr AK, Mekasha S, Petrovic DM, Varnai A, Eijsink VGH J Biol Chem. 2021 Dec;297(6):101421. doi: 10.1016/j.jbc.2021.101421. Epub 2021 , Nov 17. PMID:34798071[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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