Description: S-adenosylmethionine (SAM) is a substrate for methyl transfers to various biomolecules that yields S-adenosylhomocysteine (SAH). SAH is then hydrolyzed to homocysteine and adenosine, which is converted to methionine, and ultimately back to SAM. SAH can act as a methylation inhibitor, therefore the SAM/SAH ratio, or methylation potential, is important for maintaining proper methylation in the cell. Our S-Adenosylmethionine (SAM) and S-Adenosylhomocysteine (SAH) ELISA Combo Kit is designed for detection and quantitation of both SAM and SAH in plasma, serum, lysates, or biological fluid samples. This assay is a competitive ELISA where samples and an anti-SAM or anti-SAH antibody are added to a plate coated with a SAM or SAH conjugate. The sample and conjugate compete for antibody binding, which generates a reverse curve. Samples with high SAM and SAH levels will bind the majority of the antibody, which gets washed away and results in a low OD, while samples with low SAM and SAH levels will leave more antibody available to bind to the conjugate, producing a high signal.