CS Human

Citrate synthase is a crucial enzyme in the citric acid cycle (Krebs cycle), which is fundamental for cellular respiration in nearly all living cells. This enzyme catalyzes the synthesis of citrate from oxaloacetate and acetyl coenzyme A, marking the first step of the citric acid cycle .

Citrate synthase is located within the mitochondrial matrix of eukaryotic cells. Despite its mitochondrial function, it is encoded by nuclear DNA and synthesized using cytoplasmic ribosomes. Once synthesized, it is transported into the mitochondrial matrix where it becomes functional . The enzyme’s activity is often used as a quantitative marker for the presence of intact mitochondria .

The enzyme catalyzes the following reaction:

$$\text{acetyl-CoA} + \text{oxaloacetate} + \text{H}_2\text{O} \rightarrow \text{citrate} + \text{CoA-SH}$$

This reaction is essential for the continuation of the citric acid cycle, which is pivotal for energy production in cells .

Recombinant human citrate synthase is produced using various expression systems, such as E. coli or baculovirus-insect cells. The recombinant protein typically includes a polyhistidine tag to facilitate purification. For instance, a recombinant human citrate synthase produced in E. coli consists of 462 amino acids and has a molecular mass of approximately 51.4 kDa .

Recombinant citrate synthase is widely used in biochemical research to study mitochondrial function and energy metabolism. It is also employed in various assays to measure the activity of the citric acid cycle and to investigate mitochondrial integrity and function .

Recombinant citrate synthase is generally provided as a lyophilized powder, which is stable for up to twelve months when stored at -20°C to -80°C. It is recommended to aliquot the protein to avoid repeated freeze-thaw cycles, which can degrade the protein .