Purification and Properties of the Endo-1,4-β-glucanase from Bacillus subtilis

SUMMARY: Carboxymethylcellulase (endo-1,4-β-glucanase; EC 3.2.1.4) was purified from the culture filtrate of Bacillus subtilis AU-1 by (NH4)2SO4 precipitation, Avicel affinity chromatography, DEAE Sephadex G-75 chromatography and Sulphopropyl Sephadex C-50 chromatography. The enzyme was purified 36-fold and had an M r of 23000 as determined by gel filtration on a Sephadex G-75 column. The pH optimum of the purified enzyme was 5·5; the enzyme was stable at 65°C. Activity of the purified enzyme was significantly reduced by Cu2+, Pb2+, Sn2+, Ag+, Hg2+ and Fe2+, but was increased by 139·5% in the presence of Co2+. Inhibition studies indicated that the purified enzyme was either a metalloprotein or required certain metal ions for activation/stabilization; that iron was not a prosthetic group of the enzyme; that a tryptophanyl group was not involved in enzyme action; and that reduced thiol groups were required for enzyme activity and involved in the active site of the enzyme. The K m of the purified enzyme for carboxymethylcellulose was 4 mg ml-1, and the V max for carboxymethylcellulose hydrolysis was 0·42 mg d-glucose min-1 (mg protein)-1.