Transglutaminase

Transglutaminases, known as meat glue in food processing, are a family of enzymes (EC 2.3.2.13) that catalyze the formation of a covalent bond between a free amine group (e.g., protein- or peptide-bound lysine) and the gamma-carboxamid group of protein- or peptide-bound glutamine. Bonds formed by transglutaminase exhibit high resistance to proteolytic degradation.

Transglutaminases were first described in 1959.^[1]. The exact biochemical activity of transglutaminases was discovered in blood coagulation protein factor XIII in 1968.^[2]

Physiological transglutaminases

Eight transglutaminases have been characterised.^[3]

Mechanism of action

Transglutaminases form extensively cross-linked, generally insoluble protein polymers. These biological polymers are indispensable for the organism in order to create barriers and stable structures. Examples are blood clots (coagulation factor XIII), as well as skin and hair. The catalytic reaction is generally viewed as being irreversible and must be closely monitored through extensive control mechanisms.^[3] A collection of the transglutaminase substrate proteins and interaction partners is accessible in the TRANSDAB database.

Role in disease

Deficiency of factor XIII (a rare genetic condition) predisposes to hemorrhage; concentrated enzyme can be used to correct the abnormality and reduce bleeding risk.^[3]

Antibodies to tissue transglutaminase are found in celiac disease and may play a role in the small bowel damage in response to dietary gliadin that characterises this condition.^[3] In the related condition dermatitis herpetiformis, in which small bowel changes are often found and which responds to dietary exclusion of gliadin-containing wheat products, epidermal transglutaminase is the predominant autoantigen.^[5]

Recent research indicates that sufferers from neurological diseases like Huntington's,^[6] and Parkinson's^[7] may have unusually high levels of one type of transglutaminase, tissue transglutaminase. It is hypothesized that tissue transglutaminase may be involved in the formation of the protein aggregates that causes Huntington's disease, although it is most likely not required.^[8][3]

Industrial and culinary applications

In commercial food processing, transglutaminase or 'meat glue' is used to bond proteins together. Examples of foods made using meat glue include imitation crabmeat, fish balls, and Chicken McNuggets. It is produced by Streptomyces mobaraensis fermentation in commercial quantities or extracted from animal blood,^[9] and is used in a variety of processes, including the production of processed meat and fish products. It can be used as a binding agent to improve the texture of protein-rich foods such as surimi or ham.^[10]

Transglutaminase is also used in molecular gastronomy to meld new textures with existing tastes.

The best-known brand of culinary transglutaminase is Activa TG, made by Ajinomoto.

Transglutaminase can be used in these applications:^{[citation needed]}

• Binding small chunks of meats into a big one ("portion control"), such as in sausages, hot dogs, restructured steaks
• Improving the texture of low-grade meat such as so-called "PSE meat" (pale, soft, and exudative meat, whose characteristics are attributed to stress and a rapid postmortem pH decline)
• Making milk and yogurt creamier
• Making noodles firmer

Besides these mainstream uses, transglutaminase has been used to create some unusual foods. British chef Heston Blumenthal is credited with the introduction of "meat glue" into modern cooking. Wylie Dufresne, chef of New York's avant-garde restaurant wd~50, was introduced to transglutaminase by Blumenthal, and invented a "pasta" made up of over 95% shrimp thanks to transglutaminase.^[11]

See also

• Surimi
• Boneless Fish

References

External links

• Enzyme for Binder and Texture improver
• Ajinomoto Co's Transglutaminase Activa