PURIFICATION AND CHARACTERIZATION OF A NEW XYLANASE (XYLANASE-B) PRODUCED BY STREPTOMYCES-LIVIDANS 66

A new extracellular xylanase produced by Streptomyces lividans 66 was isolated from a genetically engineered clone of that strain. This enzyme, named xylanase B, has an M(r) of 31000 and acts specifically on xylan as an endo-type xylanase producing short-chain xylo-oligosaccharides. The activity is optimal at pH 6.5 and at a temperature of 55°C, which is similar to that of the previously characterized xylanase A. Xylanase B is glycosylated and has a pI of 8.4; its K(m) and V(max.) values are 3.71 mg/ml and 1.96 mmol/mg of enzyme respectively. Specific antibodies raised against xylanase A show no cross-reaction with xylanase B; however, the anti-(xylanase B) antibodies react slightly with xylanase A. A comparison of the hydrolysis products obtained from oat-spelts xylan with both enzymes show that xylanase A preferentially degrades short-chain oligo-xylosides, whereas xylanase B acts on the longer, water-insoluble, molecules.