Glucose isomerase

Other functions

There is evidence that phosphoglucose isomerase acts as a molecular messenger. It is produced and secreted by white blood cells, and acts to regulate the growth of several different cell types.


A deficiency of phosphoglucose isomerase is responsible for 4% of the hemolytic anemias due to glycolytic enzyme deficiencies.

Prokaryotic bifunctional glucose-6-phosphate isomerase

In some archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

 and bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 glucose-6-phosphate isomerase (PGI) activity occurs via a bifunctional enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that also exhibits phosphomannose isomerase (PMI) activity. Though not closely related to eukaryotic PGIs, the bifunctional enzyme is similar enough that the sequence
Sequence (biology)
A sequence in biology is the one-dimensional ordering of monomers, covalently linked within in a biopolymer; it is also referred to as the primary structure of the biological macromolecule.-See also:* Protein sequence* DNA sequence...

 includes the cluster of threonine
Threonine is an α-amino acid with the chemical formula HO2CCHCHCH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar...

s and serine
Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...

s that forms the sugar phosphate-binding site in conventional PGI. The enzyme is thought to use the same catalytic mechanism
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

s for both glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 ring-opening and isomerisation
In chemistry isomerisation is the process by which one molecule is transformed into another molecule which has exactly the same atoms, but the atoms are rearranged e.g. A-B-C → B-A-C . In some molecules and under some conditions, isomerisation occurs spontaneously...

 for the interconversion of glucose 6-phosphate to fructose 6-phosphate
Fructose 6-phosphate
Fructose 6-phosphate is fructose sugar phosphorylated on carbon 6 . The β-D-form of this compound is very common in cells. The vast majority of glucose and fructose entering a cell will become converted to this at some point...


External links

  • Glucose-6-phosphate isomerase in PROSITE
    PROSITE is a protein database. It consists of entries describing the protein families, domains and functional sites as well as amino acid patterns, signatures, and profiles in them. These are manually curated by a team of the Swiss Institute of Bioinformatics and tightly integrated into Swiss-Prot...

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