Diverse dextranase genes fromPaenibacillusspecies.

Genes encoding dextranolytic enzymes were isolated fromPaenibacillusstrains Dex40-8 and Dex50-2. Single, similar but non-identicaldex1genes were isolated from each strain, and a more divergentdex2gene was isolated from strain Dex50-2. The protein deduced from the Dex40-8dex1gene sequence had 716 amino acids, with a predictedM_r of 80.8 kDa. The proteins deduced from the Dex50-2dex1anddex2gene sequences had 905 and 596 amino acids, with predictedM_r of 100.1 kDa and 68.3 kDa, respectively. The deduced amino acid sequences of all three dextranolytic proteins had similarity to family 66 glycosyl hydrolases and were predicted to possess cleavable N-terminal signal peptides. Homology searches suggest that the Dex40-8 and Dex50-2 Dex1 proteins have one and two copies, respectively, of a carbohydrate-binding module similar to CBM_4_9 (pfam02018.11). The Dex50-2 Dex2 deduced amino acid sequence had highest sequence similarity to thermotolerant dextranases from thermophilicPaenibacillusstrains, while the Dex40-8 and Dex50-2 Dex1 deduced protein sequences formed a distinct sequence clade among the family 66 proteins. Examination of sevenPaenibacillusstrains, using a polymerase chain reaction-based assay, indicated that multiple family 66 genes are common within this genus. The three recombinant proteins expressed inEscherichia colipossessed dextranolytic activity and were able to convert ethanol-insoluble blue dextran into an ethanol-soluble product, indicating they are endodextranases (EC 3.2.1.11). The reaction catalysed by each enzyme had a distinct temperature and pH dependence. [ABSTRACT FROM AUTHOR]