A REINVESTIGATION OF A SYNTHETIC PEPTIDE (TRPEPZ) DESIGNED TO MIMIC TRYPSIN

Recently, a 29-residue cyclic peptide was synthesized (TrPepz) that wa s reported to possess nearly the same catalytic activity and specifici ty as the pancreatic serine protease, trypsin, for hydrolysis of a sma ll ester substrate, N-tosyl-L-arginine methyl ester (TAME), and small and large peptides [Atassi, M. Z. & Manshouri, T. (1993) Proc. Natl. A cad Sci. USA 90, 8282-8286]. To study these results we have resynthesi zed TrPepz and a related cyclic peptide reported to possess some tryps in-like activity. The authenticity of each peptide was confirmed by ma ss spectrometry, peptide sequencing, compositional analysis, and H-1 N MR spectroscopy, However, neither peptide exhibited any detectable est erase activity or amidase activity under a variety of conditions teste d. Molecular modeling studies indicated it was possible for TrPepz to be nearly superimposed upon the active site of trypsin. However, NMR e xperiments showed the structure of the cyclic peptide to be disordered . Thus, we were unable to confirm the results of Atassi and Manshouri. Our results are consistent with the view that serine protease activit y depends not only on the presence of catalytic groups but also on the ir precise and stable alignment.