A novel thermostable α-1,3-glucanase from Streptomyces thermodiastaticus HF 3-3

Thermally stable α-1,3-glucanase HF65 was purified from culture filtrate of Streptomyces thermodiastaticus HF3-3. The molecular mass of this enzyme was estimated to be 65 kDa and 45.7 kDa by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography, respectively. The purified enzyme retained more than 50% of maximum activity even after incubation at 65°C more than 2 h. Moreover, α-1,3-glucanase HF65 was stable in the presence of chemicals like SDS, benzethonium chloride, and sodium fluoride at a concentration of 1%. The enzyme also exhibited salt tolerance at a concentration up to 20%. The observed stability of α-1,3-glucanase HF65 to salt and surfactants is a great advantage for its addition to commercial oral care products. Interestingly, the N-terminal amino acid sequence did not show any similarity to those of known α-1,3-glucanases, while the sequence of internal eight amino acid residues of this enzyme was homologous with those of mycodextranases. Nevertheless, the enzyme exhibited high specificity against α-1,3-glucan. According to these results, the enzyme purified from S. thermodiastaticus HF3-3 was classified as α-1,3-glucanase which was highly homologous to mycodextranase in amino acid sequence.