Fosfoglukoseisomeraasi

Fosfoglukoseisomeraasi, also known as glucose-6-phosphate isomerase (GPI) or phosphoglucose isomerase, is an enzyme that plays a crucial role in carbohydrate metabolism. It catalyzes the reversible interconversion of glucose-6-phosphate and fructose-6-phosphate. This reaction is a key step in both glycolysis and gluconeogenesis, the pathways for breaking down and synthesizing glucose, respectively.

In glycolysis, GPI converts glucose-6-phosphate, the product of glucose phosphorylation, into fructose-6-phosphate. This isomerization is necessary because the subsequent steps in glycolysis involve a six-carbon sugar that is cleaved into two three-carbon units. Fructose-6-phosphate is then further phosphorylated to fructose-1,6-bisphosphate, which is the substrate for the enzyme aldolase, initiating the cleavage.

Conversely, in gluconeogenesis, the pathway that synthesizes glucose from non-carbohydrate precursors, GPI catalyzes the reverse reaction, converting fructose-6-phosphate back to glucose-6-phosphate. This ensures that glucose can be formed and released into the bloodstream.

Beyond its metabolic role, GPI is also known as autocrine motility factor (AMF) or neuroleukin. In this context, it has been implicated in cell proliferation, differentiation, and migration. This dual function highlights the enzyme's diverse biological significance. Mutations in the gene encoding GPI can lead to various medical conditions, including hereditary nonspherocytic hemolytic anemia and neurological disorders.