A new recombinant endo-1,3-β-D-glucanase from the marine bacterium Formosa algae KMM 3553: enzyme characteristics and transglycosylation products analysis.

A specific endo-1,3-β-D-glucanase (GFA) gene was found in genome of marine bacterium Formosa algae KMM 3553. For today this is the only characterized endo-1,3-β-D-glucanase (EC 3.2.1.39) in Formosa genus and the only bacterial EC 3.2.1.39 GH16 endo-1,3-β-D-glucanase with described transglycosylation activity. It was expressed in E. coli and isolated in homogeneous state. Investigating the products of polysaccharides digestion with GFA allowed to establish it's substrate specificity and classify this enzyme as glucan endo-1,3-β-D-glucosidase (EC 3.2.1.39). The amino-acid sequence of GFA consists of 556 residues and shows sequence similarity of 45-85% to β-1,3-glucanases of bacteria belonging to the CAZy 16th structural family of glycoside hydrolases GH16. Enzyme has molecular weight 61 kDa, exhibits maximum of catalytic activity at 45 °C, pH 5.5. Half-life period at 45 °С is 20 min, complete inactivation happens at 55 °C within 10 min. Km for hydrolysis of laminarin is 0.388 mM. GFA glucanase from marine bacteria F. algae is one of rare enzymes capable to catalyze reactions of transglycosylation. It catalyzed transfer of glyconic part of substrate molecule on methyl-β-D-xylopyranoside, glycerol and methyl-α-D-glucopyranoside. The enzyme can be used in structure determination of β-1,3-glucans (or mixed 1,3;1,4- and 1,3;1,6-β-D-glucans) and enzymatic synthesis of new carbohydrate-containing compounds.