PTMScan® Trypsin-TPCK is provided for use with Cell Signaling Technology's patented PTMScan® protocol in the initial protein digestion step. Samples in urea lysis buffer need to be diluted to 2M or less urea prior to addition of trypsin. For a 1 mg/mL solution, dissolve 20 mg trypsin in 4 mL of 1 mM HCl prior to use. Transfer the 4 mL to a 50 mL conical tube and bring the volume up to 20 mL with 1 mM HCl. Aliquot and store at -80ºC. Consult the specific PTMScan® kit and protocol for more details on the appropriate protease before digesting any protein samples.
Store lyophilized trypsin powder at 4ºC protected from moisture. Once reconstituted, store trypsin solutions at -80ºC. Lyophilized trypsin has a shelf life of 1 year at 4º C and solutions are stable for 6 months at -80º C.
Trypsin is a serine endopeptidase derived from its inactive pancreatic zymogen, trypsinogen, when the N-terminal 6 amino acid leader sequence is enzymatically removed. Activated trypsin cleaves amide and ester bonds of lysine and arginine and is used extensively in detaching cells from culture dishes, protein sequencing, and proteomics applications.
Trypsin digests polypeptides by hydrolysis at the carboxyl side of unmodified arginine and lysine residues (1). Proteolysis is slower when the cleavage site is flanked by acidic residues and will not occur if the lysine or arginine is followed by a proline (2-5). Trypsin's activity is optimal at pH 8.0 and is inhibited to varying degrees by organophosphorus compounds such as diisopropyl fluorophosphate, as well as EDTA, aprotinin, Ag+, and benzamidine (6-8).