Citrate (pro-3S)-lyase
Citrate (pro-3S)-lyase, also known as citrate lyase, is an enzyme (EC 4.1.3.6) that catalyzes the ATP-dependent cleavage of citrate into oxaloacetate and acetyl-CoA. This reaction is a crucial step in several metabolic pathways, particularly in bacteria, where it plays a role in the citrate cycle (also known as the citric acid cycle or Krebs cycle) under anaerobic conditions or when glucose is scarce. It is also found in some eukaryotic organisms, where it can contribute to fatty acid biosynthesis.
The systematic name for this enzyme is citrate oxaloacetate-lyase ((pro-3S)-CH2COO→acetyl-CoA). The name indicates that the lyase cleaves citrate in such a way that the pro-3S carboxymethyl group of citrate becomes acetyl-CoA.
Citrate lyase is typically a complex enzyme composed of multiple subunits. The enzyme requires ATP, CoA, and a divalent cation (usually Mg2+) for its activity. The overall reaction proceeds through a series of steps involving the formation of citryl-CoA as an intermediate.
The enzyme is important in understanding the metabolic flexibility of organisms, particularly in response to different environmental conditions and nutrient availability. It is also a target for potential drug development, particularly in the context of bacterial infections.