TGase

Transglutaminases (TGases) are a family of enzymes that catalyze covalent crosslinks between proteins. They form ε-(γ-glutamyl) lysine isopeptide bonds by transferring an acyl group from a glutamine residue to a lysine residue or to primary amines, thereby crosslinking proteins and altering texture, stability, and solubility. Most TGases are calcium-dependent and found across animals, plants, and microbes. They can also catalyze deamidation of glutamine to glutamic acid under certain conditions.

The best-studied mammalian member is tissue transglutaminase (TG2), a multifunctional enzyme located in the cytosol, nucleus, and extracellular matrix. TG2 participates in extracellular matrix stabilization, cell adhesion, wound healing, and signaling. Autoantibodies to TG2 are a key diagnostic marker for celiac disease, and TG2 can deamidate gliadin peptides, increasing their immunogenicity in susceptible individuals.

A widely used industrial enzyme is microbial transglutaminase (MTGase), produced by Streptoverticillium mobaraense. MTGase crosslinks a broad range of proteins and is valued in the food industry for improving texture, binding, emulsification, and gelation in products such as processed meats, dairy blends, surimi, and gluten-free foods. MTGase generally functions under relatively mild conditions and often does not require added calcium.

Other TGases occur in different tissues and organisms. In humans, other isozymes (TG1–TG7) participate in skin formation, hair, and other processes, with TG2 being the most ubiquitous. Regulation of TGase activity involves calcium levels, guanine nucleotide binding, pH, redox state, and post-translational modifications. Safety and regulation: MTGase-containing ingredients are widely used under food additive regulations; labeling and consumer concerns vary by jurisdiction.