1DLI

Bacterial UDP-glucose dehydrogenase is essential for the formation of the antiphagocytic capsule that protects many virulent bacteria from the host's immune system. The homodimeric enzyme is composed of an N-terminal NAD⁺ dinucleotide binding domain and a C-terminal UDP-sugar binding domain connected by a long central alpha helix.

The enzyme catalyses the NAD+ dependent oxidation of UDP-glucose to UDP-glucuronic acid. In mammals this is the substrate for UDP-glucuronosyl transferases in the liver. UDP-glucuronosyl transferases catalyse the formation of glucuronide conjugates with various substances e.g. bilirubin - aiding its excretion.

The active site contains residues contributed from the N- and C-terminal domains as well as from the central alpha-helix. Thr118 from the N-terminal forms a hydrogen bond to an ordered active site water molecule, that may be critical for the catalytic mechanism. Ser117 and Pro120 are also probably essential for proper orientation of the catalytic Thr118. The central alpha-helix contributes two active site residues; Lys204 and Asn208. Glu141 forms a hydrogen bond to the key catalytic residue Lys204. The C-terminal contributes two residues; Cys260 and Asp264, both having direct roles in the enzyme mechanism.