The use of a Glutamic Acid Specific Endopeptidase in Peptide Synthesis

Abstract

The readily available glutamic acid specific endopeptidase from Bacillus licheniformis, belonging to the serine group, has been investigated for its applicability in synthesis of Glu-Xaa peptide bonds. The enzyme catalyzes the aminolysis of peptide esters: Z-Glu-X was synthesized from Z-Glu-OBzl (substrate) and X (nucleophile) with X = amino acid amides, amino acid esters as well as di-and tripeptides and their C-terminal esters and amides. With the exception of H-Pro-NH₂, which was not accepted as a nucleophile, fairly high yields (>70%) were obtained in most cases. The enzyme also catalyzes condensation reactions in the presence of 60-80% water-miscible solvent: Z-Ala-Glu-Val-NH₂ was synthesized in a yield of 80% from Z-Ala-Glu-OH and H-Val-NH₂. With the synthetic polypeptide substrate ABz-Ala-Phe-Ala-Phe-Glu-Val-Phe-Tyr(NO₂)-Asp-OH and X (amino acid amides or peptide amides) as nucleophiles the transpeptidation products ABz-Ala-Phe-Ala-Phe-Glu-X were synthesized in yields of 65-95%. The results suggest that this glutamic acid specific enzyme could become an important tool in the synthesis of glutamic acid containing peptides and in particular for the modification of peptides obtained by fermentation with genetically manipulated microorganisms.

Key Words:

• Peptide syntheis
• endopeptidase
• glutamic acid
• transpeptidation