Santa Cruz Biotechnology offers an expansive library of transfected lysates that overexpress kinases and phosphatases. A protein kinase is an enzyme that modifies other proteins by chemically adding phosphate groups from high-energy donor molecules, such as ATP, through a process called phosphorylation. This usually results in a structural and/or functional change of the substrate and changes its enzyme activity, cellular location, or association with other proteins. Kinases are known to regulate the majority of cellular pathways, especially those involved in signal transduction, glucose metabolism, cell proliferation, apoptosis, transcription, and cell migration. A phosphatase is an enzyme that hydrolyses phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group, thus removing phosphate groups from proteins. This is the opposite action from a kinase, though phosphatases regulate similar pathways. Phosphatases are grouped into two main categories: metalloenzymes, which are dependent on the presence of two or more metal ions in their active sites for activity, and non-metalloenzymes. Transfected lysates that express kinases and phosphatases offer a reliable means to evaluate antibody quality and serve as excellent positive controls for experiments involving antibodies.