syntetase

Syntetase, commonly spelled synthetase in current biochemical usage, is an enzyme that catalyzes a ligation reaction in which two substrates are joined to form a larger molecule, typically with the consumption of energy from ATP or another nucleotide triphosphate. In most enzymes with the -synthetase suffix, the reaction involves activating a substrate with the energy of ATP and then forming a new bond to another molecule. The term is often used for enzymes belonging to the ligase family (EC class 6).

Many well-known synthetases participate directly in metabolism and protein synthesis, including aminoacyl-tRNA synthetases, which charge tRNA molecules with specific amino acids for translation, and various acyl-CoA synthetases that form acyl-CoA thioesters from fatty acids and coenzyme A.

Mechanistically, these enzymes typically operate via an energy-rich intermediate such as aminoacyl-AMP or acyl-AMP, created by ATP consumption, before transferring the activated group to the acceptor substrate. Some synthetases can use GTP or another nucleotide as the energy source. In contrast, the related term synthase refers to enzymes that catalyze bond formation without directly using ATP hydrolysis; the distinction is historical and not always strict, and the names can be misleading in some cases.

Common examples include aminoacyl-tRNA synthetases, glutamine synthetase, and acetyl-CoA synthetase. The spelling syntetase is a common misspelling; the standard term is synthetase.