Transglutaminase in Invertebrates

In mammals, transglutaminases play roles in a variety of essential functions, including blood coagulation, skin formation, and signal transduction, by catalyzing the isopeptide bond formation between Lys and Gln residues to form e-(γ-glutamyl) lysine bonds between appropriate substrates. Similarly, in invertebrates, such as the horseshoe crab Tachypleus tridentatus, the crayfish Pacifastacus leniusculus, and the fruit fly Drosophila melanogaster, transglutaminase is conserved and exhibits pleiotropic functions. In 1993, the first report of a nucleotide sequence of the intracellular transglutaminase in T. tridentatus was made. Today, the functions of invertebrate transglutaminases are widely investigated using biochemical and genetic techniques. Here we review the existing knowledge of invertebrate transglutaminases with an emphasis on the importance of various physiological properties in innate immune reactions.