Esterase

Esterases are a broad class of hydrolase enzymes that catalyze the cleavage of ester bonds through hydrolysis. They act on a wide range of substrates, from simple synthetic esters to complex biological esters, and play roles in digestion, metabolism, and detoxification. Esterases are distinct from lipases, which preferentially act on triglycerides, and from amidases, which hydrolyze amide bonds.

In mammals, major esterase families include the cholinesterases, such as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), which hydrolyze choline esters and regulate neurotransmission. The carboxylesterases (CES1, CES2 and related enzymes) hydrolyze a broad spectrum of carboxylic esters, including many xenobiotics and drugs. Additional esterases, such as arylesterases, contribute to ester metabolism. These enzymes collectively influence the pharmacokinetics and detoxification of numerous compounds.

Most esterases are serine hydrolases and operate via a catalytic mechanism that typically features a serine residue forming a transient acyl-enzyme intermediate, with histidine and an acidic residue (such as aspartate or glutamate) facilitating catalysis. Water then hydrolyzes the acyl-enzyme intermediate to release products and regenerate the active site.

Physiological and clinical relevance includes roles in digestion, endogenous metabolism, and the detoxification and activation of drugs and pesticides. Alterations in esterase activity can affect drug response and susceptibility to toxins. Esterase activity is measured in clinical diagnostics and is a target of inhibitors used in therapy and, in some contexts, as indicators of exposure to organophosphates and related compounds. Industrially, esterases are exploited as biocatalysts for synthesis and environmental remediation.