1,3-β-Glucanases fromStreptomyces sp.1228 lytic enzyme system

Summary

Four 1,3-β-glucanases GI, GII, GIV and GVIII from a culture filtrate ofStreptomyces sp. 1228 were purified by anion exchange chromatography using DEAE-Sepharose Cl-6B or DEAE-Cellulose, gel filtration on Bio-Gel P-200 or Sephacryl S-200, Amicon ultrafiltration and preparative PAGE. The M_r of these enzymes were 19000, 74000, 78000 and 56000 respectively. The glucanase GVIII consisted of two subunits. The optimal catalytic activity of the purified preparations was at 50–55°C and pH 5.5–6.0. The enzymes were also most stable at this pH. Both glucanases GI and GVIII were characterized by high thermostability. The glucanases showed different affinities towards laminarin with Km values of 6.65 x 10⁻⁵ mol/l for GI, 2.35 x 10⁻⁴ mol/l for GII, 8.1 x 10⁻⁵mol/l for GIV and 8.1 x 10⁻⁴mol/l for GVIII. The presence of metal ions was not required for activity of these enzymes but thiol groups increased their activity. D-glucono-δ-lactone did not inhibit the enzymes.