Escherichia coli and other enteric bacteria contain two closely related D-tagatose 1,6-bisphosphate (TagBP)-specific aldolases involved in catabolism of galactitol (genes gatY gatZ) and of N-acetyl-galactosamine and D-galactosamine (genes kbaY, kbaZ, also called agaY, agaZ). The catalytic subunits GatY/KbaY alone are sufficient to show aldolase activity and contain most or all of the residues that have been identified as essential in substrate/product recognition and catalysis for class II aldolases. However, these aldolases differ from other Class II aldolases (which are homodimeric enzymes) in that they require subunits GatZ/KbaZ for full activity and for good in vivo and in vitro stability. The Z subunits alone do not show any aldolase activity. This entry represents GatZ and KbaZ subunits. This entry also includes the D-tagatose 6-phosphate 4-epimerase Atu3167 from Agrobacterium fabrum which catalyzes the epimerization of D-tagatose 6-phosphate to D-fructose 6-phosphate. It should be noted that the previous suggestion of a tagatose 6P-kinase function for other members of this family has been debated.
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