Glucose-6-phosphate isomerase (GPI), alternatively known as
phosphoglucose isomerase (PGI) or
phosphohexose isomerase (PHI), is an
enzyme that in humans is encoded by the
GPI gene on chromosome 19. This gene encodes a member of the glucose phosphate isomerase protein family. The encoded protein has been identified as a moonlighting protein based on its ability to perform mechanistically distinct functions. In the
cytoplasm, the gene product functions as a glycolytic enzyme (glucose-6-phosphate isomerase) that interconverts
glucose-6-phosphate (G6P) and
fructose-6-phosphate (F6P). Extracellularly, the encoded protein (also referred to as neuroleukin) functions as a neurotrophic factor that promotes survival of skeletal motor neurons and sensory neurons, and as a lymphokine that induces
immunoglobulin secretion. The encoded protein is also referred to as autocrine motility factor (AMF) based on an additional function as a
tumor-secreted
cytokine and
angiogenic factor. Defects in this gene are the cause of nonspherocytic hemolytic anemia, and a severe enzyme deficiency can be associated with hydrops fetalis, immediate neonatal death and neurological impairment.
Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2014]