sugar 3,4-ketoisomerase QdtA and related proteins, cupin domain
This family includes cupin domains of several bacterial proteins homologous to sugar 3,4-ketoisomerases. Thermoanaerobacterium thermosaccharolyticum QdtA catalyzes a key step in the biosynthesis of these sugars, the conversion of thymidine diphosphate (dTDP)-4-keto-6-deoxyglucose to dTDP-3-keto-6-deoxyglucose. In Aneurinibacillus thermoaerophilus, TDP-4-oxo-6-deoxy-alpha-D-glucose-3,4-oxoisomerase (also known as FdtA) is involved in the biosynthesis of dTDP-Fucp3NAc (3-acetamido-3,6-dideoxy-alpha-d-galactose), which is part of the repeating units of the glycan chain in the S-layer. Shewanella denitrificans bifunctional ketoisomerase/N-acetyltransferase (also known as FdtD) is involved in the third and fifth steps in the production of 3-acetamido-3,6-dideoxy-alpha-d-galactose or Fuc3NAc; the C-terminal cupin domain harbors the active site responsible for the isomerization reaction. Proteins in this family belong to the cupin superfamily with a conserved "jelly roll-like" beta-barrel fold capable of homodimerization.
Comment:The four-coordinate metallocenter usually includes three histidines and one glutamate; however, proteins in this subfamily may bind metal via different amino acids
Jiyao W et al.(2023). "The conserved domain database in 2023.",