Transglutaminase reaction

Iwami, K. and Yasumoto, K. 1986. Amino-binding capacities of food proteins in transglutaminase reaction and digestibility of wheat gliadin with s-attached lysine. J. Sci. Food Agric. 37, 495-503. 

A transglutaminase reaction was found to be useful in the preparation of neoglycoproteins. For example, oo-amino glycosides were used as a substrate for transglutaminase for the addition of carbohydrates to glutamine side chains (35, 36). The success of this reaction, however, seems somewhat unpredictable. 

Chanyongvorakul, Y. et al., Physical properties of soy bean and broad bean 11S globulin gels formed by transglutaminase reaction, J. Food Sci., 60, 883, 1995. 

Several hypotheses could explain the large apparent size of VERL. Like muscle titin, VERL could be encoded by a single giant mRNA. VERL subunits could be linked together after their synthesis by a transglutaminase reaction. VERL s size... 

In order to control the size of proteins in the water-insoluble fractions, they were solubilised in 2% SDS Aen analysed by gel filtration (results not shown). This analysis clearly showed the apparition of proteins of molecular weight higher than 2 10 which are generated by Ae transglutaminase reaction. 

Transglutaminase reactions, (a) Acyl transfer, (b) Cross-linking of Glu and Lys residues in proteins or peptides, (c) Deamidation... 

Factor XIII. Factor XIII circulates in the blood as a zymogen composed of two pairs of different polypeptide chains designated A and B. Inert Factor XIII has a molecular weight of 350,000 daltons and is converted to its active transglutaminase form in the presence of thrombin and calcium. Activated Factor XIII, Xllla, induces an irreversible amide exchange reaction between the y-glutamine and S-lysine side chains of adjacent fibrin... 

An alternative to modifying the functional group attached to fibrils is to utilise the chemistry present in the amino acid side chains. Furthermore, as peptides often undergo specific modification by enzymes in vivo, these could be harnessed for synthetic purposes. Qll (Ac-QQKFQFQFEQQ-Am, a fibril-forming peptide based on Pi 1-2), was coupled to lysine-based molecules by treatment with an enzyme (tissue transglutaminase, TGase) which results in a reaction between lysine and glutamine side chains [72] (Fig. 32). 

The Derivative, 5-(biotinamido)pentylamine, contains a 5-carbon cadaverine spacer group attached to the valeric acid side chain of biotin (Thermo Fisher). The compound can be used in a carbodi-imide reaction process to label carboxylate groups in proteins and other molecules, forming amide bond linkages (Chapter 3, Section 1). However, the main use of this biotinylation reagent is in the determination of factor XHIa or transglutaminase enzymes in plasma, cell, or tissue extracts. 

The most important reaction in blood clotting is the conversion, catalyzed by thrombin, of the soluble plasma protein fibrinogen (factor 1) into polymeric fibrin, which is deposited as a fibrous network in the primary thrombus. Thrombin (factor 11a) is a serine proteinase (see p. 176) that cleaves small peptides from fibrinogen. This exposes binding sites that spontaneously allow the fibrin molecules to aggregate into polymers. Subsequent covalent cross-linking of fibrin by a transglutaminase (factor Xlll) further stabilizes the thrombus. 

An enzyme reaction intermediate (Enz—O—C(0)R or Enz—S—C(O)R), formed by a carboxyl group transfer (e.g., from a peptide bond or ester) to a hydroxyl or thiol group of an active-site amino acyl residue of the enzyme. Such intermediates are formed in reactions catalyzed by serine proteases transglutaminase, and formylglyci-namide ribonucleotide amidotransferase . Acyl-enzyme intermediates often can be isolated at low temperatures, low pH, or a combination of both. For acyl-seryl derivatives, deacylation at a pH value of 2 is about 10 -fold slower than at the optimal pH. A primary isotope effect can frequently be observed with a C-labeled substrate. If an amide substrate is used, it is possible that a secondary isotope effect may be observed as welF. See also Active Site Titration Serpins (Inhibitory Mechanism)... 

These transglutaminase-catalysed reactions can be nsed to modify the functional properties of food proteins. Transglutaminase has been nsed to catalyze the cross-hnking of a nnmber of proteins, such as whey proteins, soy proteins, glnten, myosin and... 

Fig. 1. Basic scheme of fibrin polymerization and fibrinolysis. The clot is formed on the conversion of fibrinogen to fibrin by cleavage of the fibrinopeptides by thrombin, followed by stabilization of the network with isopeptide bonds by the transglutaminase Factor XHIa. The clot is dissolved through proteolysis by the enzyme plasmin, which is activated on the fibrin surface by plasminogen activators. This process is controlled by several inhibitory reactions (black arrows).

Fibrin polymerization is initiated by the enzymatic cleavage of the fibrinopeptides, converting fibrinogen to fibrin monomer (Fig. 1). Then, several nonenzymatic reactions yield an orderly sequence of macromolec-ular assembly steps. Several other plasma proteins bind specifically to the resulting fibrin network. The clot is stabilized by covalent ligation or crosslinking of specific amino acids by a transglutaminase, Factor XHIa. 

Reduction of milk allergenicity is possible by a cross-linked reaction of milk proteins with microbial transglutaminase (m-TG) (Wroblewska et al. 2008). Diary products thus obtained possessed better functional properties with weaker syneresis and stronger curd. Also, the organoleptic properties of yoghurt prepared with m-TG make a favorable impression on potential allergic consumers. 

Nielson, P.M. 1995. Reactions and potential industrial applications of transglutaminase— Review of the literature and patents. Food Biotechnology 9 119-156. 

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