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Isopeptide bond between lysine and aspartate/asparagine. An isopeptide bond is a type of amide bond formed between a carboxyl group of one amino acid and an amino group of another. An isopeptide bond is the linkage between the side chain amino or carboxyl group of one amino acid to the α-carboxyl, α-amino group, or the side chain of another ...
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]
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.
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 ...
[4] [5] The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, as in asparagine and glutamine. It can be viewed as a derivative of a carboxylic acid ( R−C(=O)−OH ) with the hydroxyl group ( −OH ) replaced by an amino group ( −NR′R″ ); or ...
This polarised residue lowers the pKa of the cysteine, allowing it to perform a nucleophilic attack on the isopeptide bond between the ubiquitin C-terminus and the substrate lysine. Metalloproteases coordinate zinc ions with histidine, aspartate and serine residues, which activate water molecules and allows them to attack the isopeptide bond ...
An isopeptide bond is formed between the carboxyl group (COO −) of the ubiquitin's glycine and the epsilon-amino group (ε-NH + 3) of the substrate's lysine. [16] Trypsin cleavage of a ubiquitin-conjugated substrate leaves a di-glycine "remnant" that is used to identify the site of ubiquitylation.
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]