Hydrolytic cleavage of pyroglutamyl-peptide bond. III. A highly selective cleavage in 70% methanesulfonic acid.

A method for highly selective cleavage of pGlu-peptide linkages in 70% methanesulfonic acid (MSA) is described. When pGlu-Ala-Phe-OH, pGlu-His-Pro-Oh and dog neuromedin U-8 (d-NMU-8) (1--7)-OH (pGlu-Phe-Leu-Phe-Arg-OH) were hydrolyzed in 70% MSA at 60 degrees C for 3 h or at 25 degrees C for 3 d, the pGlu-peptide linkage was predominantly cleaved to give H-Ala-OH, H-His-Pro-OH and H-Phe-Leu-Phe-Arg-Pro-Arg-OH, in high yields. The results indicated that pGlu-peptide linkages are highly susceptible to 70% MSA, whereas the amide bond of the pyrrolidone moiety of the pGlu residue and other internal peptide bonds are extremely resistant.