抄録
A β-1, 3-xylan was prepared by sodium hydroxide extraction from seaweeds of Bryopsis maxima and Caulerpa sp. The seaweed xylan obtained contains xylose residues only and β-1, 3-linkage was characterized by the method of 13C-NMR spectroscopy and methylation analysis. A strain of Aspergillus terreus A-07 isolated from soil produced an endo-β-1, 3-xylanase, decomposing β-1, 3-xylan to D-xylose and D-xylooligosaccharides. Six different xylanases in the culture filtrate of A. terreus A-07 have been found and purified to homogeneity from 40- to 95-fold by ammonium sulfate fractionation, SP-Sephadex C-25 ion exchange chromatography, Biogel P-100 gel filtration, and isoelectric focusing. Each of the purified enzymes gave a single band on polyacrylamide disc gel electrophoresis, indicating that all of the purified β-1, 3-xylanases were electrophoretically homogeneous.
The six kinds of purified enzymes on SDS polyacrylamide gel electrophoresis indicated that two of the β-1, 3-xylanases have molecular weights of 11, 000, another two of the β-1, 3-xylanases have molecular weights of 14, 500, and the last two β-1, 3-xylanases have molecular weights of 13, 500 and 20, 000. The pH optima of the β-1, 3-xylanases were from 4.0 to 5.5. The optimum temperature for activity was from 40 to 55°C. All of the enzyme activities of the six β-1, 3-xylanases were inhibited by Hg2+, Mn2+, and N-bromosuccinimide. With respect to the hydrolysis patterns, the purified β-1, 3-xylanases hydrolyzed β-1, 3-xylan to xylose and xylooligosaccharides. The β-1, 3-xylanases hydrolyzed β-1, 3-xylan and rhodymenan but did not hydrolyze β-1, 4-xylan, cellulose powder, laminaran, β-1, 3-xylobiose or β-1, 3-xylotriose. By their action patterns and substrate specificities, all of the six purified enzymes were endo-type β-1, 3-xylanases.
