PURIFICATION AND SOME PROPERTIES OF INTRACELLULAR ALPHA-L-ARABINOFURANOSIDASE FROM ASPERGILLUS-NIGER 5-16

Alpha-L-arabinofuranosidase was purified from a cell-free extract of Aspergillus niger 5-16 by chromatographies on DEAE-Toyopearl, SP-Toyopearl, Ultro-gel AcA 44, Mono P, and TSK-Gel G3000SW. The final preparation thus obtained showed a single band on SDS-polyacrylamide gel electrophoresis. The molecular weight and isoelectric point were 67,000 by SDS-polyacrylamide gel electrophoresis and pH 3.5 by isoelectric focusing. The alpha-L-arabinofuranosidase contained amino acids in the order of Asx > Gly > Ala > Thr > Glx = Ser. The enzyme had maximum activity at pH 4.0 and 60-degrees-C, and was stable from pH 4 to 7 and at temperatures up to 30-degrees-C. The enzyme activity was not affected considerably by either metal ions or chemical reagents. The enzyme released arabinose from p-nitrophenyl-alpha-L-arabinofuranoside, O-alpha-L-arabinofuranosyl-(1-->3)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose, and arabinan, but not from O-beta-D-xylopyranosyl-(1-->4)-O-[alpha-L-arabinofuranosyl-(1-->3)]-O-beta-D-xylopyranosyl (1-->4)-D-xylopyranose, O-beta-D-xylopyranosyl-(1-->2)-O-alpha-L-arabinofuranosyl-(1-->3)-O-beta-D-xylopyranosyl (1-->4)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose, gum arabic, or arabinoxylan. The limit of hydrolysis of arabinan was about 58% even when the enzyme was sufficiently in excess.