alpha-galactosidase of the marine bacterium Pseudoalteromonas sp. KMM 701

An alpha-galactosidase that inactivates the group specificity of B erythroc ytes (group III) of human blood and does not affect A erythrocytes (group I I) was isolated from the marine bacterium Pseudoalteromonas sp. KMM 701. Th e enzyme preparation did not contain lectin, hemolytic, sialidase, endoglyc anase, or glycosidase activities. The enzyme is stable at 20 degrees C for 24 h, has pH optimum for catalysis within the range of 6.7-7.7, and is stab le to high concentrations of NaCl. It is 4-fold more efficient than the alp ha-galactosidase from green coffee beans. At pH 7.0 the K-m for p-nitrophen yl-alpha-D-galactopyranoside is 0.29 mM. The molecular weight of the enzyme determined by gel-filtration is 195 +/- 5 kD. The alpha-galactosidase is d enatured by urea and guanidine hydrochloride. Its activity does not depend on the presence of metal ions. It contains a sulfhydryl group essential for its catalytic activity.