tiolientsyymi

Tiolientsyymi, or thioesterases, are enzymes that act on thioester bonds found in thioester-containing substrates such as acyl-CoA thioesters. Their primary reaction is hydrolysis of the thioester to yield a free carboxylic acid and coenzyme A (CoA-SH), but many thioesterases can also catalyze trans-thioesterification, transferring the acyl group to another acceptor. They comprise diverse enzyme families with different structural folds and catalytic mechanisms.

A common and well-studied group are the acyl-CoA thioesterases (ACOTs), which regulate cellular levels of CoA and free fatty acids by hydrolyzing various acyl-CoA thioesters. In addition, thioesterase domains are integral components of larger biosynthetic systems, such as polyketide synthases (PKS) and nonribosomal peptide synthetases (NRPS), where they can catalyze the release of the final product from the carrier protein via hydrolysis or cyclization. The active sites of thioesterases vary between families; many function as serine hydrolases or as metal-dependent hydrolases, and their mechanisms reflect the diversity of substrates they encounter in metabolism and biosynthesis.

Tiolientsyymit are found across bacteria, plants, and animals, indicating broad roles in lipid metabolism, detoxification, and secondary metabolite production. In animals, ACOT enzymes help maintain CoA pools and regulate fatty acid metabolism; in plants and microbes, thioesterases participate in lipid remodeling and the formation of bioactive natural products. Beyond basic biology, thioesterases are relevant to biotechnology and metabolic engineering for the production of free fatty acids and other valuable compounds.