PURIFICATION AND CHARACTERIZATION OF 2 XYLANASES AND AN ARABINOFURANOSIDASE FROM ASPERGILLUS-SOJAE

Two isoenzymes of xylanase (endo-1,4-beta-xylanase, EC 3.2.1.8) and an arabinofuranosidase (alpha-L-arabinofuranosidase, EC 3.2.1.55) were p urified as electrophoretically homogeneous proteins from a solid-state culture of Aspergillus sojae. The molecular weights of the xylanases (X-I and X-II-B) and arabinofuranosidase (X-II-A) were estimated to be 32,700, 35,500 and 34,300, respectively, by sodium dodecyl sulfate-po lyacrylamide gel electrophoresis (SDS-PAGE). Gel filtration chromatogr aphy gave molecular weight values similar to those obtained by SDS-PAG E for each of the purified enzymes. The isoelectric points of X-I and X-II-B were 3.50 and 3.75, and that of X-II-A was 3.90. The maximum ve locities of arabinoxylan degradation by the xylanases were attained at 60 degrees C (X-I) and 50 degrees C (X-II-B), when the PPI was mainta ined at 5.5. The xylanases were stable from pH 5.0 to 8.0, and up to 5 0 degrees C (X-I) and 35 degrees C (X-II-B). The optimum pH and temper ature of X-LT-A were 5.0 and 50 degrees C, respectively, and it was st able from pH 5.0 to 9.0 and up to 50 degrees C. The activity of these three enzymes was significantly inhibited by Mn2+ and EDTA, and stimul ation by metal ions was not observed. Amino acid composition and seque nce of the amino-terminus indicated that the xylanases of A. sojae wer e distinct from other known Aspergillus xylanases.