Modification of C-Terminal

The terminal functionalization of a peptide has a very important effect on its biochemical properties. Peptides can be modified at the C-terminus with a carbonyl group. The specific modification of the C-terminus can prolong the in vivo metabolic half-life of the peptide, reduce the immunogenicity or reduce the toxic side effects. Efficient and accurate C-terminal modification of peptides is a hot field in the research of biologically active macromolecules, and it is also an urgently needed technology in the industrial production of peptides.

• Amidation

Chemically synthesized peptides usually have a free amino group (N-terminus) and a free carboxyl group (C-terminus). Amidated peptide means that the C-terminus of the peptide is amidated, and the free carboxyl-terminus is modified into an amide. C-terminal amidation can reduce the overall charge of the peptide, but may reduce the solubility of the peptide. End blocking of the peptide brings it closer to the parent protein because it increases the stability of the peptide. Therefore, the C-terminal amidation of the peptide may enhance the biological activity of the peptide.

C-Terminal Amidation

• Esterification

Acylation of amino groups and esterification of carboxyl groups are important reactions of amino acids and peptides. Esterification of peptides refers to the reaction of the carboxyl groups and alcoholic hydroxyl groups of peptides to form relatively stable ester compounds. Polyethylene glycol (PEG) is a commonly used esterification reagent and is a hydrophilic and uncharged polymer. Usually, PEG with a relative molecular mass greater than 10,000 is selected to carry out C-terminal esterification modification of the peptide under mild conditions. C-terminal esterification of peptides is beneficial to improve the biological activity of peptides and improve their stability.

• Aldolylation

Aldolylation of peptides is carried out at the C-terminus of the peptide, and the carboxyl group is modified into an aldehyde group. Peptide aldehydes are a class of peptide analogs with an aldehyde group at the C-terminus. Peptide aldehyde can simulate the transition state of the substrate when it is hydrolyzed by the enzyme during the interaction with the enzyme, and become an inhibitor of many corresponding important enzymes in the organism.

• Alcoholylation

The reduction of carbonyl groups can generate alcohol groups. Peptidols with a hydroxyl group at the C-terminus can be synthesized by reducing amino acids with unprotected side chain hydroxyl groups in the peptide sequence.

• AMC Modification

AMC (7-amino-4-methylcoumarin) is a widely used fluorescent reagent. AMC can be modified at the C-terminus of the peptide sequence. The C-terminal AMC modification process of the peptide is as follows: (1) AMC is connected with the first amino acid at the C-terminal of the peptide sequence through a condensation reaction. (2) Use solid-phase synthesis to synthesize the entire peptide chain except the first amino acid at the C-terminus, retaining the side chain of the peptide and all protective groups at the N-terminus. (3) The previously synthesized AMC-modified amino acid is subjected to a condensation reaction with the peptide chain by a liquid-phase method. (4) Deprotection, and finally complete the AMC modification of the peptide chain. AMC-modified peptides can be applied to the identification and trace determination of enzymes, the preparation of laser dyes, and the like.

AMC modification of peptides

• AFC Modification

AFC (7-amino-4-trifluoromethylcoumarin) is a fluorescent reagent. Compared with AMC, AFC has longer absorption and fluorescence wavelengths. AFC-modified peptides can be used as fluorescent substrates for the detection of enzymatic activity.

• PNA Modification

PNA (peptide nucleic acid) is a synthetic nucleic acid-like chemical. The backbone of PNA is composed of repeating N-2-(aminoethyl)-glycine units, which are combined through peptide bonds. Similar to peptides, PNAs also have N- and C-termini. Since PNA is neither a peptide nor a nucleic acid. Therefore, PNA is very stable and is not easily hydrolyzed by proteases or nucleases. At the same time, due to the strong pairing specificity between bases, the thermal stability of PNA is high.

View Our List of PNA Monomers >

• CMK Modification

With the increasing application of peptide drugs in the treatment of diseases, simple molecular peptide chains can no longer meet the increasingly in-depth scientific research requirements of researchers. People began to try to introduce halogen elements such as F and Cl into peptide molecules. Chloromethyl ketone modification (CMK modification) has greatly changed the biological properties of peptide molecules and significantly promoted the development of peptide drugs.

• FMK Modification

Fluoromethylketone-modified peptides (FMK-modified peptides) are a class of inhibitors that inhibit the activity of specific enzymes. Such peptides can also be used to explore the active reaction site of the enzyme and to analyze the three-dimensional structure of the enzyme.

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