Synthesis and properties of Cbz-Phe-Arg-CHN2 (benzyloxycarbonylphenylalanylarginyldiazomethane) as a proteinase inhibitor.

The preparation of peptides terminating in -Arg-CHN2 has been attempted because of their potential value as proteinase inactivators. We have succeeded in one case, converting Cbz-Phe-ArgOH to the diazomethane without blocking the guanidino group. As expected from previous results with such reagents, the new derivative was extremely effective in inactivating a cysteine proteinase specific for cleaving at arginyl bonds, that is, clostripain. However, in contrast with the inertness of serine proteinases to reagents of this type in the cases examined previously, plasma kallikrein was inactivated by Cbz-Phe-Arg-CHN2, although with a considerably lower rate constant than with clostripain. Trypsin, however, was not inactivated, but gradually destroyed the reagent, as had been observed previously with chymotrypsin and Cbz-Phe-CHN2. This has now been re-examined with rho-nitro-Cbz-Ala-Phe-CHN2 and shown to involve a cleavage to rho-nitro-Cbz-Ala-PheOH, probably with liberation of diazomethane.