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EC Number

Catalytic Site Atlas

CSA LITERATURE entry for 1hxq

E.C. nameUDP-glucose---hexose-1-phosphate uridylyltransferase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz)
CSA Homologues of 1hxq1gup,1guq,1hxp,1r3a,1vkv,1z84,1zwj,2q4h,2q4l,
CSA Entries With UniProtID P09148
CSA Entries With EC Number
PDBe Entry 1hxq
PDBSum Entry 1hxq
MACiE Entry M0088

Literature Report

IntroductionNucleotidyltransferases catalyse the covalent modification of a variety of biological molecules. These reactions are crucial for the synthesis of coenzymes, cyclic nucleotides, polynucleotides, and nucleotide sugars. These reactions involve substitutions at the R -phosphorus of a nucleotidyl donor substrate and result in displacement of a phosphoryl ester or pyrophosphate. Substrates for such reactions may include nucleoside di- or triphosphates, as well as nucleotide sugars, such as UDP-Glc. Galactose-1-phosphate uridylyltransferase (hexose-1-phosphate uridylyltransferase) catalyses the exchange of the UMP moiety between the hexose 1-phosphates of Glc and Gal and their corresponding UDP-sugar. The enzyme is distinct among nucleotidyl transferases that use phosphates as acceptor groups in that it is the only one that does not utilise nucleoside di- or triphosphates as the nucleotidyl donor substrate. The reaction is part of the Leloir pathway of galactose metabolism required for the normal equilibration of UDP-hexoses among most organisms. Deficiencies in uridylyltransferase activity culminate in the metabolic disease galactosemia, which occurs as an autosomal recessive trait.
MechansimNote there is a divalent iron and zinc metal cofactors present however although essential for enzymatic activity they are not involved in catalysis. HIS 166 in the active site of the the enzyme in Escherichia coli attacks the alpha-phosphorus of UDP--Glc, displaces Glc-1-P, and forms the high energy covalent uridylyl-enzyme (UMP-enzyme) intermediate, which then reacts with Gal-1-P to produce UDP-Gal.

Catalytic Sites for 1hxq

Literature References

Notes:Role of Asn153 not essential.