Transglutaminases are enzymes that catalyze the crosslinking of proteins by epsilon gamma glutamyl lysine isopeptide bonds. While the primary structure of transglutaminases is not conserved, they all have the same amino acid sequence at their active sites and their activity is calcium dependent. Transglutaminase 3 consists of two polypeptide chains activated from a single precursor protein by proteolysis. Transglutaminase 3 is involved the later stages of cell envelope formation in the epidermis and hair follicle.