α-Galactosidase from Diplococcus pneumoniae

α-Galactosidase, free from neuraminidase, β-glucosaminidase, and β-galactosidase, was isolated from the culture broths of Diplococcus pneumoniae. The enzyme was found to be stable in 0.1 M NaCl solution, but unstable at lower ionic strength and sensitive to p-chloromercuribenzoate, cupric sulfate, and mercuric chloride. The optimal pH of this enzyme preparation was found to be between 5.6 and 6.0. The α-galactosidase readily liberated galactose from melibiose, raffinose, and stachyose. It also attacked o-nitrophenyl-α- d-galactopyranoside; however, β- l-arabinopyranoside and lactose were not hydrolyzed by this enzyme. The pneumococcal α-galactosidase preparation also possessed transglycosylase activity. When melibiose was incubated with this enzyme, 4 new sugar spots were detected on paper chromatogram. One of these spots contained galactose and glucose in a ratio of 1:2 and had the same mobility as manninotriose on paper chromatogram. Upon incubation of raffinose with α-galactosidase, a sugar with the mobility of stachyose was detected in the digests. Incubation of stachyose with this enzyme also resulted in the appearance of a spot with mobility slower than stachyose.