Preferentially cleaves alpha-1,3 and alpha-1,4 glycoside linkages. Involved in the hydrolysis of the galactomannan, it splits alpha-linked galactose moieties. It is particularly suitable for the hydrolysis of guar gum to a gum with improved gelling properties. Can cleave terminal alpha-1,3-linked galactose residues responsible for blood group B specificity from the surface of erythrocytes thereby converting these cells serologically to group O. Hydrolysis of terminal, non-reducing alpha-D-galactose residues in alpha-D-galactosides, including galactose oligosaccharides, galactomannans and galactolipids. Used to convert human blood group antigens of type B into type O, the universal donor type. Belongs to the glycosyl hydrolase 27 family.