It has been shown [1,2,E1] that the following glycosyl hydrolases can be, on the basis of sequence similarities, classified into a single family:

• Escherichia coli and Bacillus subtilis α-galactosidase (EC 3.2.1.22) (melibiase) (gene melA).
• Thermotoga maritima α-glucosidase (EC 3.2.1.20) (gene aglA).
• Probable 6-phospho-β-glucosidases (EC 3.2.1.86) (gene celF) from Escherichia coli and Bacillus subtilis.
• Maltose-6'-phosphate glucosidases (EC 3.2.1.122) (6-phospho-α-D- glucosidase) from Bacillus subtilis (gene glvG) and Fusobacterium mortiferum (gene malH).
• Bacillus subtilis protein lplD.

These enzymes require NAD and a divalent ion for their activity. They are proteins of about 50 Kd. As a signature pattern we selected a conserved region located in the central section. This region does not contain residues directly shown to be important for the catalytic activity.