Glycoside Hydrolases Family 4; Phospho-beta-glucosidase.
Some bacteria simultaneously translocate and phosphorylate disaccharides via the phosphoenolpyruvate-dependent phosphotransferase system (PEP-PTS). After translocation, these phospho-disaccharides may be hydrolyzed by the GH4 glycoside hydrolases such as the phospho-beta-glucosidases. Other organisms (such as archaea and Thermotoga maritima ) lack the PEP-PTS system, but have several enzymes normally associated with the PEP-PTS operon. The 6-phospho-beta-glucosidase from Thermotoga maritima hydrolylzes cellobiose 6-phosphate (6P) into glucose-6P and glucose, in an NAD+ and Mn2+ dependent fashion. The Escherichia coli 6-phospho-beta-glucosidase (also called celF) hydrolyzes a variety of phospho-beta-glucosides including cellobiose-6P, salicin-6P, arbutin-6P, and gentobiose-6P. Phospho-beta-glucosidases are part of the NAD(P)-binding Rossmann fold superfamily, which includes a wide variety of protein families including the NAD(P)-binding domains of alcohol dehydrogenases, tyrosine-dependent oxidoreductases, glyceraldehyde-3-phosphate dehydrogenases, formate/glycerate dehydrogenases, siroheme synthases, 6-phosphogluconate dehydrogenases, aminoacid dehydrogenases, repressor rex, and NAD-binding potassium channel domains, among others.