Sintetasa

Sintetasa, or synthase in English, is an enzyme that catalyzes the synthesis of a product from simpler substrates, typically by forming a new covalent bond. A defining feature is that many synthases do not require direct energy input from ATP or other nucleotide triphosphates to drive the reaction. This contrasts with synthetases (often called ligases), which rely on energy from ATP or another triphosphate to form bonds between two substrates.

The distinction between synthases and synthetases is historical and not absolute; some enzymes labeled as synthases may couple to energy changes within the substrates, while some enzymes called synthetases catalyze steps that resemble synthase reactions. Despite this, the term synthase remains useful for describing bond-forming enzymes that operate without explicit ATP consumption.

Examples include citrate synthase, a key enzyme of the citric acid cycle that condenses acetyl-CoA with oxaloacetate to form citrate, and sucrose synthase, which participates in sucrose formation in plants by transferring a glycosyl unit from UDP-glucose to fructose or another acceptor. Synthases occur across metabolic pathways, contributing to the assembly of biomolecules such as lipids, carbohydrates, and other metabolites.

In nomenclature, usage can vary by language and tradition, and some enzymes retain historic names that reflect older classifications. When energy usage is central to the reaction, the terms synthetase or ligase may be preferred.