PRINCIPAL CHARACTERISTICS OF ALPHA-GALACTOSIDASE FROM LEUCONOSTOC-MESENTEROIDES SUBSP MESENTEROIDES

alpha-Galactosidases (alpha-gal) from six strains of Leuconostoc mesen teroides subsp. mesenteroides, which were isolated from four different ecological niches, have been characterized. The enzymes have an optim um pH ranging from 5.5 to 6.4. Strain 19A possesses a pH optimum close to neutral. The optimum temperature varied with the strains, ranging from 37 to 43 degrees C. The K-m values of the enzymes for substrate p -nitrophenyl-alpha-D-galactopyranoside (PNPG) varied from 2.15 to 22.7 0 mM. alpha-Gal from strain 23A had the lowest affinity for substrate PNPG. An increase of the affinity for PNPG in the presence of 10 mM la ctose was observed for strains 6M, 19A, 23A, 19M, while this higher af finity for PNPG was also observed in the presence of 10 mM galactose f or strains 6M, 23A, 19M. The activation energy of the enzyme from diff erent strains was calculated to be about 62.9 - 72.8 kJ/mol. Ca2+ ions have a strong inhibitive effect on the enzyme activity. Appearance of alpha-gal activity band and protein profiles under the same condition s of SDS-PAGE allowed an estimation of the apparent molecular weight o f alpha-gal to be at about 175,000.