ENO2

ENO2, also known as gamma-enolase or neuron-specific enolase (NSE), is a gene that encodes a neuron-specific enzyme belonging to the enolase family. It is expressed predominantly in neurons and neuroendocrine cells, with lower levels in other tissues. ENO2 is one of three mammalian enolase genes, the others being ENO1 (alpha-enolase, ubiquitous) and ENO3 (beta-enolase, muscle).

Biochemical role and properties: Neuron-specific enolase is a cytosolic metalloenzyme that catalyzes the reversible conversion of 2-phosphoglycerate to phosphoenolpyruvate in glycolysis, a reaction that requires divalent metal ions such as Mg2+. The enzyme typically functions as a dimer and contributes to cellular energy production in neurons.

Clinical significance: NSE is widely used as a biomarker of neuronal damage and neuroendocrine tumors. In serum or cerebrospinal fluid, elevated levels can indicate brain injury, stroke, or neurodegenerative processes; in oncology, high NSE levels are associated with neuroendocrine tumors, particularly small cell lung carcinoma and neuroblastoma. Immunohistochemical detection of ENO2 in tumor tissues helps identify neuronal or neuroendocrine differentiation, though its specificity is limited and it is usually interpreted alongside other markers.

Genetics and evolution: ENO2 expression is developmentally regulated and enriched in the nervous system. The enzyme is highly conserved among vertebrates, reflecting its fundamental role in energy metabolism.