InterPro domain: IPR000941

Enolase (2-phospho-D-glycerate hydrolase) is an essential, homodimeric enzyme that catalyses the reversible dehydration of 2-phospho-D-glycerate to phosphoenolpyruvate as part of the glycolytic and gluconeogenesis pathways [ 1 , 2 ]. The reaction is facilitated by the presence of metal ions [ 3 ]. In vertebrates, there are 3 different, tissue-specific isoenzymes, designated alpha, beta and gamma. Alpha is present in most tissues, beta is localised in muscle tissue, and gamma is found only in nervous tissue. The functional enzyme exists as a dimer of any 2 isoforms. In immature organs and in adult liver, it is usually an alpha homodimer, in adult skeletal muscle, a beta homodimer, and in adult neurons, a gamma homodimer. In developing muscle, it is usually an alpha/beta heterodimer, and in the developing nervous system, an alpha/gamma heterodimer [ 4 ]. The tissue specific forms display minor kinetic differences. Tau-crystallin, one of the major lens proteins in some fish, reptiles and birds, has been shown [ 5 ] to be evolutionary related to enolase.

Neuron-specific enolase is released in a variety of neurological diseases, such as multiple sclerosis and after seizures or acute stroke. Several tumour cells have also been found positive for neuron-specific enolase. Beta-enolase deficiency is associated with glycogenosis type XIII defect.

1. Characterization of a maize cDNA that complements an enolase-deficient mutant of Escherichia coli. Plant Mol. Biol. 16, 787-95
2. Molecular structure of the human muscle-specific enolase gene (ENO3). Biochem. J. 275 ( Pt 2), 427-33
3. A carboxylate oxygen of the substrate bridges the magnesium ions at the active site of enolase: structure of the yeast enzyme complexed with the equilibrium mixture of 2-phosphoglycerate and phosphoenolpyruvate at 1.8 A resolution. Biochemistry 35, 4349-58
4. Enolase isoenzymes in adult and developing Xenopus laevis and characterization of a cloned enolase sequence. Biochem. J. 251, 31-9
5. Recruitment of enzymes as lens structural proteins. Science 236, 1554-6