A4 beta-galactosidase middle domain: a type 1 glutamine amidotransferase (GATase1)-like domain. A4 beta-galactosidase middle domain: a type 1 glutamine amidotransferase (GATase1)-like domain. This group includes proteins similar to beta-galactosidase from Thermus thermophilus. Beta-Galactosidase hydrolyzes the beta-1,4-D-galactosidic linkage of lactose, as well as those of related chromogens, o-nitrophenyl-beta-D-galactopyranoside (ONP-Gal) and 5-bromo-4-chloro-3-indolyl-beta-D-galactoside (X-gal). This A4 beta-galactosidase middle domain lacks the catalytic triad of typical GATase1 domains. The reactive Cys residue found in the sharp turn between a beta strand and an alpha helix termed the nucleophile elbow in typical GATase1 domains is not conserved in this group.
Beta-galactosidase trimerisation domain. This is non catalytic domain B of beta-galactosidase enzymes belong to the glycosyl hydrolase 42 family. This domain is related to glutamine amidotransferase enzymes, but the catalytic residues are replaced by non functional amino acids. This domain is involved in trimerisation.
Type 1 glutamine amidotransferase (GATase1) domain found in Cobyric Acid Synthase (CobQ). Type 1 glutamine amidotransferase (GATase1) domain found in Cobyric Acid Synthase (CobQ). CobQ plays a role in cobalamin biosythesis. CobQ catalyses amidations at positions B, D, E, and G on adenosylcobyrinic A,C-diamide in the biosynthesis of cobalamin. CobQ belongs to the triad family of amidotransferases. Two of the three residues of the catalytic triad that are involved in glutamine binding, hydrolysis and transfer of the resulting ammonia to the acceptor substrate in other triad aminodotransferases are conserved in CobQ.