ALPHA-GALACTOSIDASE FROM THE YEAST TORULASPORA DELBRUECKII IFO-1255

The yeast Torulaspora delbrueckii IFO 1255 was selected as the strain fermenting melibiose from 35 strains of Torulaspora species. The strai n IFO 1255 produced extracellular and cell-associated forms of alpha-g alactosidase when grown on either melibiose or galactose as the sole c arbon source. Most of the enzyme was located outside of the cell membr ane: the periplasmic space, or cell walls, or both. alpha-Galactosidas e was purified to homogeneity from the cell-free extract of the strain IFO 1255 by acid treatment and column chromatography on DEAE-Toyopear l 650M and Butyl-Toyopearl 650M. The molecular weight of the purified enzyme was estimated to be 88 000 by SDS-polyacrylamide gel electropho resis and 530 000 by gel filtration. The enzyme contained 50% of its m olecular weight as carbohydrate. Optimum pH and temperature were 4.5-5 .5 and 55 degrees C, respectively. The enzyme was inhibited strongly b y Ag2+, Hg2+ and Cu2+ each at 1 mmol l(-1). The K-m (mmol l(-1)) for p -, o-, m-nitrophenyl alpha-D-galactopyranoside, melibiose, raffinose a nd stachyose were 2.8, 1.3, 2.8, 4.2, 170 and 230, respectively, and V -max (mu mol min(-1) mg protein(-1)) for those substrates were 310, 14 0, 21, 22, 30 and 44, respectively. The properties of alpha-galactosid ase from T. delbrueckii IFO 1255 were similar to those from the relate d species, Saccharomyces cerevisiae.