Abstract:Dextranase can specifically hydrolyze the α-(1,6) glycosidic bond in dextran, and it has important applications in food industrial production and prevention of dental caries. It is mainly derived from microorganisms. The marine bacterium Catenovulum sp. DP03 was screened and the complete genome sequence was determined. The dextranase genes were cloned and heterologous expressed in Escherichia coli. Then the properties of recombinant dextranases were compared and analyzed. There were two dextranases genes found in DP03, i.e., GL002870 and GL002872 which were 2 511 bp and 2 805 bp, respectively. The 3D structure of Cadex2870 and Cadex2872 were similar to that of AoDex. The catalytic regions Q418-D440 of AoDex corresponded to Q431-D453 of Cadex2870 and Q425-D447 of Cadex2870, respectively. The enzyme activities of Cadex2870 and Cadex2872 were 16.2 U/mg and 4.0 U/mg, respectively. The optimum catalytic temperatures for Cadex2870 and Cadex2872 were 45 ℃ and 30 ℃ respectively and the optimum catalytic pH values were 7 and 8, respectively. The products of Cadex 2870 hydrolyzed dextran were maltoheptaose, maltopentaose, maltotetraose and a small amount of maltose. And the hydrolysates of Cadex2872 were maltoheptaose, maltopentose and maltotetraose. The marine bacterium Catenovulum sp. DP03 contained two genes encoding dextranase. The two dextranases were different in the protein structure and enzymatic properties.
