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Amide bonds, and thus isopeptide bonds, are stabilized by resonance (electron delocalization) between the carbonyl oxygen, the carbonyl carbon, and the nitrogen atom. The bond strength of an isopeptide bond is similar to that of a peptide due to the similar bonding type. The bond strength of a peptide bond is around 300 kJ/mol, or about 70 kcal ...
Isopeptide bonds occur in the linkage of protein amino acid side chains to proteins such as ubiquitin and SUMO in the protein degradation pathway. In eukaryotes, enzymes with isopeptidase activity are often involved in this pathway; all five classes of deubiquitinating enzymes have isopeptidase activity. [ 1 ]
Bonds formed by transglutaminase exhibit high resistance to proteolytic degradation (proteolysis). [2] The reaction is [1] Gln-(C=O)NH 2 + NH 2-Lys → Gln-(C=O)NH-Lys + NH 3. Transglutaminases can also join a primary amine ( RNH 2 ) to the side chain carboxyamide group of a protein/peptide bound glutamine residue thus forming an isopeptide ...
Autocatalytic cycle of formose reaction showing how glyceraldehyde can be both the catalyst and the product of one portion of this complex reaction type. An early example of autocatalysis is the formose reaction , in which formaldehyde and base produce sugars and related polyols.
HTL has been reported to form isopeptide bonds with lysine residues in substrate proteins, a post-translational modification known as N-homocysteinylation (N-hcy). This causes protein damage via a thiyl radical mechanism. [2]
A first kinetically controlled product rearranges to form the amide bond. The most common form of native chemical ligation uses a peptide thioester that reacts with a terminal cysteine residue. [58] Other methods applicable for covalently linking polypeptides in aqueous solution include the use of split inteins, [59] spontaneous isopeptide bond ...
When the isopeptag is bound to a target protein, it spontaneously binds its binding partner through an isopeptide bond, an amide bond formed autocatalytically.The reaction is robust and occurs at various temperatures from 4-37 °C, a pH range of 5–8, and in the presence of commonly used detergents.
Peptide bond formation via dehydration reaction. When two amino acids form a dipeptide through a peptide bond, [1] it is a type of condensation reaction. [2] In this kind of condensation, two amino acids approach each other, with the non-side chain (C1) carboxylic acid moiety of one coming near the non-side chain (N2) amino moiety of the other.