Abstract
Transglutaminases (TGases) are enzymes able to catalyze acyl-transfer reactions introducing covalent cross-links between proteins, peptides and primary amines. Animal TGases were the first studied and are divided in nine different groups of isoenzymes. They have a wide range of functions in the metabolism of most animal cells, and share the characteristic of being Ca2+-dependent. Microbial and plant TGases were also identified, and there is a vast heterogeneity among their amino acid sequences. Interestingly, it seems that all transglutaminases share a specific amino acid triad of Cys-His-Asp in their catalytic site, which can be found in all tertiary structures of the enzymes yet studied so far. Microbial TGases are the most widely used for food modification due to lower costs and high yields involved with their extraction and purification when compared to mammal sources. TGases are ubiquitously found in a variety of plants, and their utilization for food transformation has been proposed. However, there is only a single attempt using vegetal TGase in food systems, where apple pomace was used to improve the quality of pork meat. The transference of mammalian TGase genes to plants has also been considered and they were found to be successfully expressed in rice and tobacco leaves. These results lead to a new approach, where TGases could be literally farmed for food utilization.
Highlights
Transglutaminase (TGase) activity was first observed by Clarke et al (1957) when they found an enzyme with transamidating properties in guinea-pig liver
The reaction can happen in the presence of primary amines, what can cause the incorporation of polyamines in proteins (Folk et al, 1980)
The hypothesis includes the possible deamidation of certain glutamine residues of gliadin by tissue transglutaminases (tTGase), which can be recognized as epitopes by T-cells, leading to the inflammatory disease (Skovbjerg et al, 2002)
Summary
Transglutaminase (TGase) activity was first observed by Clarke et al (1957) when they found an enzyme with transamidating properties in guinea-pig liver. Many transglutaminases have been well characterized in terms of structural and catalytic properties (Kim et al, 1991; 1993; Della Mea et al, 2004) This group of enzymes shares the capacity of catalyzing acyl-transfer reactions introducing covalent cross-links between proteins (Nonaka et al, 1989), peptides and primary amines (Folk et al, 1980). Until the early 90’s, the only commercial source of transglutaminase was derived from guinea-pig liver, and had a complicated method of separation and purification resulting in high prices (Zhu et al, 1995) It was in the late 80’s that TGase activity was firstly described from Streptoverticillium species (Aldo et al, 1989), what caused a revolution in the commercialization of the enzyme. The most extensively studied TGases and their features are reviewed, especially those derived from plants
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