Serine protease inhibitor mediated peptide bond re-synthesis in diverse protein molecules

► Protease inhibitor, PMSF mediated peptide re-synthesis. ► Fast religation of peptides in the presence of a small molecule. ► X-ray structure of a nicked protein. Protease inhibitors have been extensively used in research to prevent unwanted degradation of proteins during purification and analysis. Here, we report a remarkable discovery of protease inhibitor mediated reformation of peptide bonds by the serine protease inhibitor, PMSF in a diverse set of proteolyzed molecules. Interestingly, the religation reaction in the presence of PMSF occurs in a very short time period and with very high yields of the religated product. We also investigate the plausible mechanism of such a reaction and demonstrate through biochemical studies and X-ray crystallography that proximity of reacting termini is essential for the feasibility of this reaction.