Structural highlights
FunctionPublication Abstract from PubMedThe recently discovered lytic polysaccharide monooxygenases (LPMOs) carry out oxidative cleavage of polysaccharides and are of major im-portance for efficient processing of biomass. NcLP-MO9C from Neurospora crassa acts both on cellu-lose and on non-cellulose beta-glucans, including cello-dextrins and xyloglucan. The crystal structure of the catalytic domain of NcLPMO9C revealed an extend-ed highly polar substrate-binding surface well-suited to interact with a variety of sugar substrates. The ability of NcLPMO9C to act on soluble substrates was exploited to study enzyme-substrate interac-tions. Electron spin resonance (EPR) studies demon-strated that the Cu2+ center environment is altered upon substrate binding, whereas isothermal titration calorimetry (ITC) studies revealed binding affinities in the low micromolar range for polymeric substrates that are in part due to the presence of a carbohydrate-binding module (a CBM1). Importantly, the novel structure of NcLPMO9C enabled a comparative study, revealing that the oxidative regioselectivity of LPMO9s (C1, C4 or both) correlates with distinct structural features of the copper coordination sphere. In strictly C1 oxidizing LPMO9s, access to the sol-vent-facing axial coordination position is restricted by a conserved tyrosine residue, whereas access to this same position seems unrestricted in C4 oxidizing LPMO9s. LPMO9s known to produce a mixture of C-1 and C4-oxidized products show an intermediate situation. Structural and functional characterization of a lytic polysaccharide monooxygenase with broad substrate specificity.,Borisova AS, Isaksen T, Dimarogona M, Kognole AA, Mathiesen G, Varnai A, Rohr AK, Payne CM, Sorlie M, Sandgren M, Eijsink VG J Biol Chem. 2015 Jul 15. pii: jbc.M115.660183. PMID:26178376[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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