Decomposition of soybean oligosaccharides by intestinal bacteria. VI. Purification and properties of .ALPHA.-galactosidase from Escherichia coli subsp. communior IAM 1272.

Abstract

Galactosylsucroses contained in soybeans are not digestible. Thus we wished to detect α-galactosidase (EC 3. 2. 1. 22) in intestinal bacteria. The strain of E. coli in the title was found to produce considerably this enzyme adaptively. We could prepare rather pure solution of the enzyme from the sonicate of the strain. It was purified about 142-fold. It showed optimum pH and temperature at 6.8 and 37°C, respectively, with the substrate p-nitrophenyl-α-D-galactoside (PNPG). Dilute enzyme solutions were very unstable even at 0_??_5°C. However, concentrated solutions were considerably stable. The Michaelis constant (M) was 1.07×10-4, 2.33×10-3, and 3.65×10-1 for PNPG, melibiose, and raffinose, respectively, The maximum velocity (mole/min/mg protein) was 2.72×10-5, 2.67×10-5, and 2.04×10-5, respectively for the same three substrates. This enzyme had a weak transferase action.