Involved in the degradation of various alpha-linked galactosides such as raffinose, stachyose and melibiose. Hydrolysis of terminal, non-reducing alpha-D-galactose residues in alpha-D-galactosides, including galactose oligosaccharides, galactomannans and galactolipids. Completely inhibited by most divalent metal cations, however magnesium and molybdene have no effect. Optimum pH is 5.0. Optimum temperature is 90 degrees Celsius. Trimer. Belongs to the glycosyl hydrolase 36 family.