Protein phosphorylation is a complex biochemical process regulated by protein kinases that catalyze the transfer of the gamma-P of ATP to a recipient protein that acts as a substrate. This post-translational modification is primarily directed onto serine, threonine, and tyrosine amino acid residues within a protein. Changes in the phosphorylation status of phosphoproteins can alter their biological function, and aberrations in signal transduction cascades have been linked to a number of diseases, including cancer, diabetes, heart disease, inflammation, and neurological disorders. Assay Designs offers a diverse portfolio of kits and antibodies for the detection of proteins modified by phosphorylation, as well as a variety of kinase activity kits and active proteins. Click here for a complete list of substrates and inhibitors for in vitro kinase assays.