Structure of β‐1,4‐mannanase from the common sea hare
β‐1,4‐Mannanase (EC 126.96.36.199) catalyzes the hydrolysis of β‐1,4‐glycosidic bonds within mannan, a major constituent group of the hemicelluloses. Bivalves and gastropods possess β‐1,4‐mannanase and may degrade mannan in seaweed and/or phytoplankton to obtain carbon and energy using the secreted enzymes in their digestive systems. In the present study, the crystal structure of AkMan, a gastropod β‐1,4‐mannanase prepared from the common sea hare Aplysia kurodai, was determined at 1.05 Å resolution. This is the first report of the three‐dimensional structure of a gastropod β‐1,4‐mannanase. The structure was compared with bivalve β‐1,4‐mannanase and the roles of residues in the catalytic cleft were investigated. No obvious binding residue was found in subsite +1 and the substrate‐binding site was exposed to the molecular surface, which may account for the enzymatic properties of mannanases that can digest complex substrates such as glucomannan and branched mannan.
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Document Type: Research Article
Publication date: 2012-10-01