The development and importance of C-terminal modification of peptides

The post-translation modification of eukaryotic proteins by the addition of isoprenyl lipids at their C-termini was first observed in the 1970s and 1980s. Since then, more than a hundred proteins are modified by C15 farnesyl or C20 geranylgeranyl groups, including most members of the Ras, Rho, and Rab families of G proteins. The C-terminal of the peptide is synthesized as an amide to neutralize the negative charge created by the C-terminal COOH. This modification is added to prevent enzyme degradation, mimic native proteins, and in some cases remove hydrogen bonding at the C-terminal of the peptides which may interfere with the assays.

• AMC (7-Amino-4-Methylcoumarin) 

Enzyme substrates based on the AMC (7-amino-4-methyl coumarin) fluorophore are popular tools for studying protease activity and specificity. In such substrates, AMC is usually linked to the peptide by forming an amide bond between the coumarin amine and the carboxyl group of the C-terminal amino acid residue.

The proteolysis of the amide bond releases free AMC, resulting in a significantly increased fluorescence. The excitation/emission wavelengths are about 342 nm/441 nm.

• Amidation

Terminal amidation (C-terminus) will remove the positive charge and help peptides imitate their natural structure. In addition, this modification makes the resulting peptide more stable towards enzymatic degradation resulting from exopeptidases.

• Biotin

Biotin has a very strong affinity for streptavidin, so the biotinylation of peptides is an effective method of specifically binding peptides to streptavidin-coated surfaces.

Peptide biotinylation can be performed at the N-terminus or C-terminus. At the C-terminus, the first-order epsilon amino group on the lysine inserted at the C-terminus is biotinylated to remove the positive charge of lysine.

source from: https://www.creative-peptides.com/services/peptide-c-terminal-modification.html