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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 ...
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.
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 ...
The N-terminal "ring" can be from 7 to 9 amino acids long and is formed by an isopeptide bond between the N-terminal amine of the first amino acid of the peptide and the carboxylate side chain of an aspartate or glutamate residue. The C-terminal "tail" ranges from 7 to 15 amino acids in length. [15]
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 ]
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.
The final step in the first ubiquitylation event is an attack from the target protein lysine amine group, which will remove the cysteine, and form a stable isopeptide bond. [6] One notable exception to this is p21 protein, which appears to be ubiquitylated using its N-terminal amine, thus forming a peptide bond with ubiquitin. [7]
USP20 belongs to the USP group and, like most DUBs, catalyse the breakage of an isopeptide bond between a lysine residue of the target protein and the terminal glycine residue of a ubiquitin protein. This occurs via a conserved cysteine and histidine residue in the catalytic site of the enzyme. The histidine molecule is protonated by the ...