Purification and characterization of two α-L-arabinofuranosidases from Streptomyces diastaticus

Abstract

A nonsporulating strain of Streptomyces diastaticus producing α-L- arabinofuranosidase activity (EC 3.2-1.55) was isolated from soil. Two α-L- arabinosidases were purified by ion-exchange chromatography and chromatofocusing. The enzymes had molecular weights of 38,000 (C1) and 60,000 (C2) and pIs of 8.8 and 8.3, respectively. The optimum pH range of activity for both enzymes was between 4 and 7. The apparent K(m) values with p- nitrophenyl arabinofuranoside as the substrate were 10 mM (C1) and 12.5 mM (C2). C1 retained 50% of its activity after 8 h of incubation at 25°C, while C2 retained 80% activity. After 3 h of incubation at 50°C, C1 lost 90% of its initial activity while C2 lost only 40%. The purified enzymes hydrolyzed p-nitrophenyl α-L-arabinofuranoside and liberated arabinose from arabinoxylan and from a debranched β-1,5-arabinan.