SUBSTRATE SPECIFICITIES OF PENICILLIUM-SIMPLICISSIMUM ALPHA-GALACTOSIDASES

The substrate specificities of three Penicillium simplicissimum ol-gal actosidases, AGLI, AGLII, and AGLIII, were determined by using various isolated galactose-containing oligosaccharides and polymeric galacto( gluco)mannans. AGLI released galactose from melibiose and raffinose-fa mily oligosaccharides brit tile amount of galactose released was decre ased from 96% to 35% by the increasing chain length of the substrate f rom raffinose to verbascose. It was able to release galactose linked t o the nonreducing end and less efficiently to the internal residues of the galactomanno-oligomers. AGLI was able to hydrolyze 60-92% of gala ctose from polymer ic galacto(gluco)mannans alone but its action was f acilitated by mannanase and beta-mannosidase. rn addition, it was able to release about 10% of the galactose from softwood kraft pulp alone and about 22% in combination with mannanase. AGLII was highly specific torc ard small galactose-containing oligosaccharides in which the gal actose is linked to the nonreducing end of the substrate. it released 90-100% of galactose present in melibiose, raffinose, stachyose, and v erbascose; however, it was able to degrade polymeric substrates only i n combination with mannanase and beta-mannosidase. AGLIII had only low activity toward the oligomeric substrates tested. It was able to rele ase some galactose from the polymeric galacto(gluco)mannans alone, but its action was clearly enhanced br the backbone degrading enzymes. (C ) 1998 Elsevier Science Inc.