Trypsin is a serine protease that preferentially cleaves the carboxyl ends of lysines and arginines. It has three known isozymes in humans: Trypsin-1 (PRSS1), Trypsin-2 (PRSS2), and Trypsin-3 (PRSS3). Porcine trypsin is commonly used in proteomic applications for digesting proteins into peptides prior to mass spectrometric analyses. Trypsin is also used in tissue culture for resuspending adherent cells. Mammalian trypsin digests at an optimal temperature around 37°C.