Enolase

Enolase is an enzyme, more particularly, an active metalloenzyme. This enzyme belongs to the family of lyases, the hydro-lyases, breaking the carbon-oxygen bonds, and is present in all tissues and organisms involved in glycolysis or fermentation. The optimal pH of this enzyme is 6.5 in humans.Its main function is to intervene in the 9th step of glycolysis (the penultimate step in this metabolic pathway), a step in which occurs the dehydration of 2-phosphoglycerate (2-PG) in phosphoenolpyruvate (PEP), a product that will be used in the next and final step for the production of energy (ATP).
Enolase has three different isoforms: the ENO1 or alpha-enolase (in muscle tissue); ENO2 or gamma-enolase or neuro specific enolase (in neurons); ENO3 or beta-enolase (in skeletal muscle cells). Enolase has a molecular weight of about 100000 Daltons (depending on the isoform). In humans, the α-enolase has two antiparallel subunits, which have two domains that establish hydrophobic interactions. The subunits interact via salt bridges, involving arginine and glutamate.
The specific enolase to neurons is released in a wide variety of diseases, such as multiple sclerosis or stroke, or myocardial infarction.
In several medical experiments, it was employed enolase concentrations in samples in an attempt to diagnose certain conditions and its severity. Several studies demonstrated that different levels of enolase may also be associated with tumor growth or with the occurrence of myocardial infarction or stroke, so it was inferred that the levels of enolase serve as an indicative of the prognostic evaluation of victims of cardiac arrest.
Enolase inhibitors have been utilized in health care for the treatment and prevention various diseases, such as anti-trypanosome drugs and more recently as anticancer agents. Enolase can be inhibited by fluoride ion (F-). The fluoride forms a complex with magnesium and phosphate, which binds to the active center of the enzyme rather than the substrate 2-PG, preventing the conversion of 2-PG into PEP, decreasing the production of PEP and, consequently, ATP.
Intake of fluoride-containing water inhibits the catalytic activity of enolase of bacteria present in oral cavity (highly dependent on glycolysis due to the anaerobic environment), interrupting glycolysis and, thus, bacterial fermentation (decreased acid production), preventing the formation of dental caries.

Text written by:
Inês Carvalho
Junjie Lin
Maria Alves
Susana Pinto
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