5o2x | pdb_00005o2x
Extended catalytic domain of H. jecorina LPMO9A a.k.a EG4
Structural highlights
FunctionLP9A_HYPJQ Lytic polysaccharide monooxygenase (LPMO) that depolymerizes crystalline and amorphous polysaccharides via the oxidation of scissile alpha- or beta-(1-4)-glycosidic bonds, yielding C1 and C4 oxidation products (PubMed:26285758, PubMed:28110665, PubMed:28900033, PubMed:30238672). 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:28900033, PubMed:32414932, PubMed:34597668). Produces both neutral and oxidized cello-oligosaccharides from cellulose (PubMed:26285758, PubMed:28900033). Acts also on soluble cello-oligosaccharides as short as a tetramer (PubMed:26285758). The oxidative activity displays a synergistic effect capable of boosting endoglucanase activity, and thereby substrate depolymerization of soy cellulose by 27% (PubMed:28110665).[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedFor decades, the enzymes of the fungus Hypocrea jecorina have served as a model system for the breakdown of cellulose. Three-dimensional structures for almost all H. jecorina cellulose-degrading enzymes are available, except for HjLPMO9A, belonging to the AA9 family of lytic polysaccharide monooxygenases (LPMOs). These enzymes enhance the hydrolytic activity of cellulases and are essential for cost-efficient conversion of lignocellulosic biomass. Here, using structural and spectroscopic analyses, we found that native HjLPMO9A contains a catalytic domain and a family-1 carbohydrate-binding module (CBM1) connected via a linker sequence. A C-terminally truncated variant of HjLPMO9A containing 21 residues of the predicted linker expressed at levels sufficient for analysis. Here, using structural, spectroscopic and biochemical analyses, we found that this truncated variant exhibited reduced binding to and activity on cellulose compared with the full-length enzyme. Importantly, a 0.95 A resolution X-ray structure of truncated HjLPMO9A revealed that the linker forms an integral part of the catalytic domain structure, covering a hydrophobic patch on the catalytic AA9 module. We noted that the oxidized catalytic center contains a Cu(II) coordinated by two His ligands, one of which has a Hisbrace in which the His1 terminal amine group also coordinates to a copper. The final equatorial position of the Cu(II) is occupied by a water-derived ligand. The spectroscopic characteristics of the truncated variant were not measurably different from those of full-length HjLPMO9A, indicating that the presence of the CBM1 module increases the affinity of HjLPMO9A for cellulose binding, but does not affect the active site. High-resolution structure of a lytic polysaccharide monooxygenase from Hypocrea jecorina reveals a predicted linker as an integral part of the catalytic domain.,Hansson H, Karkehabadi S, Mikkelsen N, Douglas NR, Kim S, Lam A, Kaper T, Kelemen B, Meier KK, Jones SM, Solomon EI, Sandgren M J Biol Chem. 2017 Sep 12. pii: jbc.M117.799767. doi: 10.1074/jbc.M117.799767. PMID:28900033[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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