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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 ...
Eventually, [these] thioesters could have served to usher in ATP through its ability to support the formation of bonds between phosphate groups. However, due to the high free energy change of thioester's hydrolysis and correspondingly their low equilibrium constants, it is unlikely that these compounds could have accumulated abiotically to any ...
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.
Splicing of group I introns is processed by two sequential transesterification reactions. [3] First an exogenous guanosine or guanosine nucleotide (exoG) docks onto the active G-binding site located in P7, and then its 3'-OH is aligned to attack the phosphodiester bond at the "upstream" (closer to the 5' end) splice site located in P1, resulting in a free 3'-OH group at the upstream exon and ...
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 ...
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]
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.