Characterization of α-1,3-glucanase isozyme from Paenibacillus glycanilyticus FH11 in a new subgroup of family 87 α-1,3-glucanase

Two α-1,3-glucanase isozymes, designated as α-1,3-glucanase 1 (Agl-FH1) and α-1,3-glucanase 2 (Agl-FH2), were purified from the culture medium of Paenibacillus glycanilyticus FH11. Agl-FH1 and Agl-FH2 exhibited similar characteristics such as optimal pH, pH stability, optimal temperature, thermostability, and molecular masses on SDS-PAGE. However, their hydrolysis products of α-1,3-glucan varied somewhat. Agl-FH1 hydrolyzed α-1,3-glucan into a mixture of maltotriose and maltotetraose, and maltotetraose was the major hydrolysis product of Agl-FH2. N-terminal amino acid sequence analysis and LC–MS/MS analysis of trypsin digested fragments revealed several differences between the amino acid sequences of Agl-FH1 and Agl-FH2. Genes of Agl-FH1 and Agl-FH2 were subcloned into an expression plasmid, and both enzymes were successfully expressed in Escherichia coli. The recombinant Agl-FH1 and Agl-FH2 exhibited the same enzymatic properties as those of each wild-type enzyme, and both of the recombinants showed the activity on the protoplast formation of Schizophyllum commune mycelia. A great diversity was detected in the C-terminal region of family 87 α-1,3-glucanases. Compared with Agl-FH2 which is highly sequence-related to the known α-1,3-glucanases, the C-terminal region of Agl-FH1 has only slight similarity to them (approximately 20% identity). Our analysis revealed that Agl-FH1 was the first member of a new subgroup of family 87 α-1,3-glucanases.