2 How it Works: The Mechanism of Gluing Proteins

Transglutaminase is an enzyme (in mammals, it is Calcium-dependent) that catalysis several acyl transfer reactions. (Keillor, J. W et al. 2014)  The glutamine residue of a protein acts as the acyl donor and either water or a primary amine (for example Lysine) becomes the acyl acceptor.

Enzymes showing transglutaminase activity is widespread in nature.   Soil bacteria, plants, invertebrates, amphibians, fish and birds. (Griffin, M., et al.,  2002)  Transglutaminase functions as biological glue in two important ways.  On the one hand, it is important in cell-matrix interaction and the general maintenance of tissue integrity through the creation of isopeptide bonds (inducing the process of cross-linking) between Glutamine and Lysine residues when the protein molecule is enriched with this amino acid.  In this case, a primary amine is the acyl acceptor of this amino acid.

The transfer of acyl onto a lysine residue bound in the polypeptide chain induces the process of cross-linking, i.e. the formation of inter- or intramolecular cross-links ε-(γ-Glu)Lys (Kieliszek, M and Misiewicz, A.  2013).

On the other hand, it plays an important role in cell death as it speeds up the chemical reaction (catalyses) of the breakdown of amino acids (deamination) “if there is an absence of free amine groups. In this case, water acts as an acyl acceptor (Motoki and Seguro 1998; Kuraishi et al. 2001). The reactions that are catalysed by this enzyme result in significant changes in the physical and chemical properties of proteins, such as modifications in viscosity, thermal stability, elasticity and resilience of proteins.”  (Kieliszek, M & Misiewicz, A.;  2013) This will also happen in the presence of excess transglutaminase.


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