Identification , Separation , and Preliminary Characterization of Invertase and , - Galactosidase in Actinomyces viscosus

The initial step of disaccharide dissimilation by Actinomyces viscosus serotype 2 strain M-100 was studied. Sucrase activity was found in the 3,000 x g particulate fraction and the 37,000 x g soluble fraction of the cells, whereas lactase activity was found almost exclusively in the 37,000 x g soluble fraction. Neither sucrase nor lactase activity was appreciable in the culture liquor. Sucrose phosphorylase, a-glucosidase, and polysaccharide synthesis activities were not observed in the soluble cell fraction. The sucrase was identified as invertase (EC 3.2.1.26; 8-n-fructofuranoside fructohydrolase). The lactase was identified as f8-galactosidase (EC 3.2.1.23; 3-i)-galactoside galactohydrolase). The enzymes in the 37,000 x g soluble fraction were separable by diethylaminoethyl-cellulose chromatography, giving one f8-galactosidase peak and one major and one minor invertase peak. Acrylamide gel electrophoresis showed different electrophoretic mobilities of the enzymes. The molecular weight of the (3-galactosidase is about 4.2 x 105 and that of invertase is about 8.6 x 104. The /galactosidase has aKm for lactose of about 6 mM and a pH optimum between pH 6.0 and 6.5. The major invertase component has aKm for sucrose of about 71 mM and a pH optimum between pH 5.8 and 6.3.