Transglutaminase enzyme

A) Caserns cross-linked by die enzyme transglutaminase within the casein micelle ... 

The weak physical forces that hold together self-assembled nanoparticles are, of course, susceptible to disruption under the influence of thermodynamic and/or mechanical stresses. Hence some workers have investigated ways to reinforce nanoscale structures via covalent bonding. For instance, improved stability of protein nanoparticles, in particular, casein micelles, can be achieved by enzymatic cross-linking with the enzyme transglutaminase, which forms bonds between protein-bound glutamine and lysine residues. By this means native casein micelles can be converted from semi-reversible association colloids into permanent nanogel particles (Huppertz and de Kruif, 2008). 

Another common crosslink is an amide formed between the y-carboxyl group of a glutamic acid side chain and an amino group from a lysine residue.307 This isopeptide linkage is formed from a residue of gluta-mine through the action of the enzyme transglutaminase (Eq. 2-23). Isopeptide crosslinks are found in hair, skin, connective tissue, and blood clots. 

Seguro, K., Nio, N., Motoki, M. 1996b. Some characteristics of a microbial protein cross-linking enzyme Transglutaminase. In Parris, N., Kato, A., Creamer, L.K., Pearce, J. (Eds.), Macromolecular Interactions in Food Technology. American Chemical Society, Washington D.C., pp. 271-280. 

Feeney and Whitaker (30, 31) have emphasized the importance of the enzymes transglutaminase, lipoxygenase, polyphenol oxidase and peroxidase in the crosslinking of proteins. With transglutaminase, chimeric proteins can be made readily by crosslinking two proteins, each with quite different properties (32, 33). 

The arARs have been shown to copurify with and activate a high molecular weight G protein, Gh, which is structurally unrelated to heterotrimeric G proteins and has been shown to be the enzyme transglutaminase II (43). This response has been shown to be activated by the a1B- and a1D-, but not the a1A-, subtypes (44). However, the functional significance of this pathway remains unclear because Gh knockout mice show no overt phenotype with respect to arAR signaling (45). 

Beside the acid and salt types of coagulants discussed above, the microbial enzyme transglutaminase has also been studied as a tofii coagulant (Tang 2007). Since it forms a structure with strong chemical bonds, the resulting tofu has a very smooth... 

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