PROSITE documentation PDOC00108Galactose-1-phosphate uridyl transferase signatures
Galactose-1-phosphate uridyl transferase (EC 2.7.7.12) (galT) catalyzes the transfer of an uridyldiphosphate group on galactose (or glucose) 1-phosphate. During the reaction, the uridyl moiety links to a histidine residue. In the Escherichia coli enzyme, it has been shown [1] that two histidine residues separated by a single proline residue are essential for enzyme activity. The first one is a ligand to a zinc ion and the second act as a nucleophile.
On the basis of sequence similarities, two apparently unrelated families seem to exist. Class-I enzymes are found in eukaryotes as well as some bacteria such as Escherichia coli or Streptomyces lividans, while class-II enzymes have been found so far only in some Gram-positive bacteria such as Bacillus subtilis or Lactobacillus helveticus [2].
We developed signature patterns for both families. For class-I enzymes the signature is based on the active site residues. For class-II enzymes we chose a region which also includes two conserved histidines.
Note:Class-I enzymes are structurally related to the HIT family of proteins (see <PDOC00694>).
Last update:December 2004 / Pattern and text revised.
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PROSITE methods (with tools and information) covered by this documentation:
| 1 | Authors | Reichardt J.K.V. Berg P. |
| Title | Conservation of short patches of amino acid sequence amongst proteins with a common function but evolutionarily distinct origins: implications for cloning genes and for structure-function analysis. | |
| Source | Nucleic Acids Res. 16:9017-9026(1988). | |
| PubMed ID | 2845364 |
| 2 | Authors | Mollet B. Pilloud N. |
| Title | Galactose utilization in Lactobacillus helveticus: isolation and characterization of the galactokinase (galK) and galactose-1-phosphate uridyl transferase (galT) genes. | |
| Source | J. Bacteriol. 173:4464-4473(1991). | |
| PubMed ID | 2066342 |
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