isozymesENO2

ENO2, also known as gamma-enolase or neuron-specific enolase (NSE), is a glycolytic enzyme belonging to the enolase family. The ENO2 gene encodes the neuron-specific enolase, which is expressed predominantly in neurons and neuroendocrine cells. It is a cytosolic enzyme that functions as a homodimer of approximately 47 kDa subunits and catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate in glycolysis, requiring Mg2+ as a cofactor. ENO2 expression is highest in the brain, retina, and certain neuroendocrine tissues; during development its expression increases as neurons mature.

In addition to its metabolic role, ENO2 serves as a clinical biomarker: neuron-specific enolase is measured in blood or CSF to assess neuronal injury after stroke, traumatic brain injury, or hypoxic events, and is used as a tumor marker in neuroendocrine cancers such as small cell lung carcinoma and neuroblastoma. Serum NSE levels help monitor disease progression and response to therapy, though specificity can be limited because ENO2 can be expressed in some non-neural tumors and other conditions can elevate NSE.

Molecularly, ENO2 belongs to the enolase family, with two other mammalian isozymes, ENO1 (α-enolase) and ENO3 (β-enolase). The three enzymes share catalytic mechanics but are differentially expressed, enabling tissue-specific regulation of glycolysis. ENO2 expression can be modulated by neuronal differentiation cues and neuronal activity.