Purification and characterization of the beta-galactosidase of Aeromonas formicans.

Rohlfing, S. R. (Western Reserve University, Cleveland, Ohio), and I. P. Crawford. Purification and characterization of the beta-galactosidase of Aeromonas formicans. J. Bacteriol. 91:1085-1097. 1966.-The beta-galactosidase of Aeromonas formicans was purified by diethylaminoethyl cellulose chromatography and gel filtration on Sephadex G-200. The properties of the enzyme molecule were compared with purified beta-galactosidase from Escherichia coli. The sedimentation coefficients and electrophoretic mobilities of the two enzymes were not significantly different; the electrophoretic mobility of urea-produced subunits of the two enzymes was also similar. The stabilities of the two enzymes to denaturing agents provided measurable differences; E. coli beta-galactosidase is relatively more heat-stable and more resistant to the action of urea. The amino acid compositions of the two proteins revealed significant differences in several amino acids, particularly alanine, arginine, glycine, and leucine. The comparisons cited suggest that A. formicans and E. coli are not completely unrelated, for their beta-galactosidases show considerable structural similarity.