Cell Biolabs’ Methionine Assay Kit measures total methionine within biological samples. Methionine and ATP are converted by s-adenosylmethionine synthetase to s-adenosylmethionine, inorganic phosphate, and pyrophosphate. Phosphoenolpyruvate and pyrophosphate are converted by phosphate pyruvate dikinase to pyruvate. Pyruvate is converted by pyruvate oxidase in the presence of phosphate and oxygen into acetyl phosphate, carbon dioxide, and hydrogen peroxide. The resulting hydrogen peroxide is then detected with a highly specific fluorometric probe. Horseradish peroxidase catalyzes the reaction between the probe and hydrogen peroxide, which bind in a 1:1 ratio. Samples are compared to a known concentration of methionine standard within the 96-well microtiter plate format. Samples and standards are incubated for 30 minutes and then read with a standard 96-well fluorometric plate reader.