EVALUATION OF CATALYTIC ACTIVITY AND SYNERGISM BETWEEN 2 XYLANASE ISOENZYMES IN ENZYMATIC-HYDROLYSIS OF 2 SEPARATE XYLANS IN DIFFERENT STATES OF SOLUBILITY

Synergism of two xylanase (1,4 beta-D-xylan xylanohydrolase, EC 3.2.1. 8) isoenzymes from Streptomyces A451 was observed in enzymic hydrolysi s of water-soluble and -insoluble fractions of two commercial xylan pr eparations. The reaction modes were determined qualitatively by TLC an d quantitatively by GLC. With oat-spelt xylan as substrate, the total amount of xylose and xylobiose produced by using xylanase I and xylana se II in sequence was significantly higher than that by xylanase I or xylanase II individually, while the amounts of the relatively higher-m olecular-weight oligosaccharides xylotriose to xylopentaose obtained b y using isoxylanases individually were more than those obtained by usi ng isoxylanases in sequence. A time-course study on the release of hyd rolysis products over a 24-h period revealed that higher oligosacchari des were released initially followed by release of simpler sugars. A s tudy of the hydrolysis of model oligosaccharides by crude enzyme prepa ration revealed a preference for higher oligosaccharides and demonstra ted that xylopentaose was hydrolyzed to xylose, xylobiose, and xylotri ose. A comparison was made of the hydrolysis of two different xylans, birchwood (hardwood) and oat-spelt (softwood), by crude xylanase. Prod uct profiles showed that there were significant differences between th e range and amounts of products released from the two different xylans . Studies on relative specific activities showed that xylanase II had overall lower specific activity toward various xylans than did xylanas e I, and xylanase I, xylanase II, and crude xylanase showed lower spec ific activity toward insoluble xylan fractions than toward soluble xyl an fractions. In addition, the reduction in specific activity was grea ter for insoluble birchwood than for insoluble oat-spelt xylan.