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Publication Abstract from PubMed

Cellvibrio japonicus is a Gram-negative soil bacterium that is primarily known for its ability to degrade plant cell wall polysaccharides through utilization of an extensive repertoire of carbohydrate-active enzymes (CAZymes). Several putative chitin degrading enzymes are also found amongst these CAZymes, such as chitinases, chitobiases and lytic polysaccharide monooxygenases (LPMOs). In the present study we have characterized the chitin-active LPMO, CjLPMO10A, a tri-modular enzyme containing a catalytic family AA10 LPMO module, a family 5 chitin-binding module and a C-terminal unclassified module of unknown function. Characterization of the latter module revealed tight and specific binding to chitin, thereby unraveling a new family of chitin-binding modules (classified as CBM73). X-ray crystallographic elucidation of the Cj LPMO10A catalytic module revealed that the active site of the enzyme combines structural features hitherto only observed in either cellulose or chitin active LPMO10s. Analysis of the copper-binding site by EPR showed a signal signature more similar to those observed for cellulose cleaving LPMOs. The full-length LPMO shows no activity towards cellulose, but is able to bind and cleave both alpha- and beta-chitin. Removal of the chitin-binding modules reduced LPMO activity towards alpha-chitin compared to the full-length enzyme. Interestingly, the full-length enzyme and the individual catalytic LPMO module boosted the activity of an endochitinase equally well, also yielding similar amounts of oxidized products. Finally, gene deletion studies show that CjLPMO10A is needed by C. japonicus to obtain efficient growth on both purified chitin and crab shell particles.

Structural and Functional Analysis of a Lytic Polysaccharide Monooxygenase Important for Efficient Utilization of Chitin in Cellvibrio japonicus.,Forsberg Z, Nelson CE, Dalhus B, Mekasha S, Loose JS, Crouch LI, Rohr AK, Gardner JG, Eijsink VG, Vaaje-Kolstad G J Biol Chem. 2016 Feb 8. pii: jbc.M115.700161. PMID:26858252^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.