Relationship Proteases - TransglutaminasesTransglutaminases catalyze the acyl transfer reaction between a γ-carboxamide group of glutamine and the ε-amino group of lysine, which results in the formation of isopeptide bonds. Human
transglutaminases possess a catalytic triad and the reaction proceeds via a reactive intermediate linked to the nucleophilic cysteine of the enzyme. The mechanism is similar to the proteolysis reaction catalyzed by thiol
proteases that possess the same catalytic triad.
Transglutaminases use a similar structural architecture as papain-like thiol
proteases and even have an evolutionary relationship.
The biology and physiology of these enzymes are closely related. For example, the
transglutaminase coagulation factor XIIIa cross-links
fibrin and therefore plays an important role in blood clot formation. The serine
protease thrombin (
T056) activates
factor XIII cleaving the activation peptide. Subsequently,
plasmin (
P012) degrades the fibrin clot. Therefore,
proteases are important tools in
transglutaminase research.