CHARACTERIZATION OF GALACTOSIDASES FROM ASPERGILLUS-NIGER - PURIFICATION OF A NOVEL ALPHA-GALACTOSIDASE ACTIVITY

Ail enzyme with P-galactosidase activity and three proteins exhibiting alpha-galactosidase activity were purified from a culture filtrate of Aspergillus niger grown on arabinoxylan. beta-galactosidase, optimall y active at pH 4 and 60-65 degrees C, was active against p-nitrophenyl -beta-D-galactopyranoside, lactose, and pectic galactan. It was not ab le to release galactose from sugar beet pectin or lemon pectin. Its ac tion on pectic galactan was increased by the presence of beta-galactan ase. The three forms of alpha-galactosidase activity that showed diffe rent molecular masses and pls were found to have the same mass after d eglycosylation with N-glycanase F and to be the same protein based on their hi-terminal amino acid sequence data. The purified alpha-galacto sidase was shown to be different from alpha-galactosidase A from A. ni ger. This confirmed the existence of at least two different alpha-gala ctosidases in A. niger. alpha-Galactosidase, optimally active at pH 4. 5 and 50-55 degrees C, was active tow ard p-nitrophenyl-alpha-D-galact opyranoside, melibiose, raffinose, stachyose, and locust bean gum, on which substrate it exhibited synergism with beta-mannanase. (C) 1998 E lsevier Science Inc.