UTP—glucose-1-phosphate uridylyltransferase

UTP—glucose-1-phosphate uridylyltransferase
File:HUDP-glucose pyrophosphorylase pymol.png UDP-glucose pyrophosphorylase pictured in pymo
Identifiers
EC number	2.7.7.9
CAS number	Template:CAS
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search PMC articles PubMed articles NCBI proteins

UTP—glucose-1-phosphate uridylyltransferase also known as glucose-1-phosphate uridylyltransferase (or UDP–glucose pyrophosphorylase) is an enzyme associated with glycogenesis. It synthesizes UDP-glucose from glucose-1-phosphate and UTP; i.e.,

glucose-1-phosphate + UTP $\rightleftharpoons$ UDP-glucose + pyrophosphate

UTP—glucose-1-phosphate uridylyltransferase is an enzyme found in yeast, plants, and mammals as it is a key player in carbohydrate metabolism. It has been studied significantly in plants as sugar metabolism and production is seen as important for understanding growth from an agricultural standpoint. Recently, human UDP-glucose pyrophosphorylase has been studied and crystallized, revealing a different type of regulation than other organisms previously studied. Its significance is derived from the many uses of UDP-Glucose including galactose usage, glycogen synthesis, glycoprotein synthesis, and glycolipid synthesis.

Examples

Human genes encoding proteins with UTP—glucose-1-phosphate uridylyltransferase activity include:

UDP–glucose pyrophosphorylase 1 Identifiers Symbol UGP1 Entrez 7359 HUGO 12526 OMIM 191750 Other data EC number 2.7.7.9 Locus Chr. 1 q21-q22

UDP–glucose pyrophosphorylase 2 Identifiers Symbol UGP2 Entrez 7360 HUGO 12527 OMIM 191760 RefSeq NM_006759 UniProt Q16851 Other data EC number 2.7.7.9 Locus Chr. 2 p14-p13

Function

In many species, UDP-glucose pyrophosphorylase occupies a central role in carbohydrate metabolism. Its product, UDP-glucose, is involved in multiple pathways and is a precursor for other sugar nucleotides. In leaves, UDP–glucose pyrophosphorylase is a key part of the sucrose biosynthesis pathway, supplying Uridine diphosphate glucose to Sucrose-phosphate synthase which converts UDP-Glucose and D-fructose 6-phosphate into sucrose-6-phosphate. It may also be partially responsible for the breakdown of sucrose in other tissues using UDP-Glucose.

Mechanism

In this enzyme’s primary reaction the phosphate group on glucose-1-phosphate replaces the phosphoanhydride bond on UTP. As this reaction is relatively common and spontaneous, the Gibbs Free Energy is close to zero, however, inorganic pyrophosphatase quickly hydrolyzes the pyrophosphate and drives the reaction forward.

Regulation

Although functionally similar across species, UDP-glucose pyrophosphorylase has different structures and regulation mechanisms in different organisms.

Plants

UDP–glucose pyrophosphorylase in plants is regulated through oligomerization and possibly phosphorylation. In barley, it has been shown that UDP-glucose pyrophosphorylase is only active in monomeric form but readily forms oligomers.

Humans

In humans, UDP-glucose pyrophosphorylase is active as an octamer. This in turn lowers the activity of human UDP-glucose pyrophosphorylase compared to yeast UDP-glucose pyrophosphorylase. The difference in structure is potentially explained by the different UDP-glucose requirements of organisms with lower organisms such as yeast requiring more UDP-glucose than higher organisms such as mammals.

Disease relevance

In humans, galactosemia is a disorder that affects the development of newborns and children as they cannot metabolize the sugar galactose properly. It is speculated that overexpression of UDP-Glucose pyrophosphorylase may relieve symptoms in humans with galactosemia. The enzyme has also been found to be required for the biosynthesis of capsular polysaccharide, an important virulence factor of streptococcus pneumoniae, a bacterial cause of pneumonia, bronchitis, and other breathing issues.

External links

• UDP Glucose Pyrophosphorylase at the US National Library of Medicine Medical Subject Headings (MeSH)