Molecular cloning and Biochemical properties of GH-16 β-agarase from Gilvimarinus agarolyticus JEA5

Abstract

Agar is complex polysaccharide founds in the cell walls of some red algae and up to 70 % of the algal cell wall can be agar polymers. Agar was formed by a mixture of two polysaccharides named agarose and agaropectin.Agarose can be hydrolyzed by α-agarase (E.C. 3.2.1.158) and by β-agarase (E.C. 3.2.1.81) the former cleaves the α-1, 3 linkage of agarose to generate agaro-oligosaccharides, and the latter cleaves the β-1,4 linkage to generate neoagaro-oligosaccharides. Agarases have been isolated from many sources, including seawater, marine sediments, marine algae, marine mollusks, fresh water and soil. Recently, Givimarinus chinensis, G. polysacchalyticus, G. agarilyticus were identified and their agarolytic activity also reported. However, there are no report published that molecular and functional characterization of agarase from Givimarinus genus. In this study, we first report molecular characterization and biochemical properties of agarase from Gilvimarinus genus.A gene (Gaa16a) encoding a β-agarase from Gilvimarinus agarolyticus JEA5 was cloned and expressed in E. coli. The recombinant protein was purified as a fusion protein and biochemically characterized. The purified recombinant agarase (rGaa16A) showed maximum activity at 55°C and pH 7. Interestingly, the thermostability of rGaa16A was improved in the presence of CaCl2 rGaa16A showed specific activity toward agarose with 103.5 unit/mg. rGaa16A highlzed by α-agarase (E.C. 3.2.1.158) and by β-agarase (E.C. 3.2.1.81) the former cleaves the α-1, 3 linkage of agarose to generate agaro-oligosaccharides, and the latter cleaves the β-1,4 linkage to generate neoagaro-oligosaccharides. Agarases have been isolated from many sources, including seawater, marine sediments, marine algae, marine mollusks, fresh water and soil. Recently, Givimarinus chinensis, G. polysacchalyticus, G. agarilyticus were identified and their agarolytic activity also reported. However, there are no report published that molecular and functional characterization of agarase from Givimarinus genus. In this study, we first report molecular characterization and biochemical properties of agarase from Gilvimarinus genus.A gene (Gaa16a) encoding a β-agarase from Gilvimarinus agarolyticus JEA5 was cloned and expressed in E. coli. The recombinant protein was purified as a fusion protein and biochemically characterized. The purified recombinant agarase (rGaa16A) showed maximum activity at 55°C and pH 7. Interestingly, the thermostability of rGaa16A was improved in the presence of CaCl2 rGaa16A showed specific activity toward agarose with 103.5 unit/mg. rGaa16A highl