The condensation of the dicarboxylate oxaloacetate and acetyl CoA to the tricarboxylate citrate is catalyzed by citrate synthase. It is within this reaction that carbon molecules (as acetyl CoA) obtained from pyruvate oxidation are fed into the tricarboxylic acid (TCA or citric acid) cycle. As a mitochondrial enzyme, citrate synthase is commonly used as a normalization factor for mitochondrial protein, but can also be used as a biomarker for mitochondrial content in a tissue homogenate. Cayman's MitoCheck® Citrate Synthase Activity Assay Kit allows for the simple and convenient determination of citrate synthase activity from isolated mitochondria or cell homogenates. This assay measures the production of SH-CoA by monitoring the absorbance of Citrate Synthase Developing Reagent at 412 nm in a convenient 96-well format.