A transglutaminase involved in the coagulation system of the freshwater crayfish, Pacifastacus leniusculus. Tissue localisation and cDNA cloning

The crayfish haemolymph can form stable and insoluble clots by a transgluta minase (TGase)-catalysed crosslinking reaction between the soluble clotting protein molecules from the plasma. The crayfish haemocytes, both semigranu lar and granular cells, as well as the muscle tissue, contain TGase activit y, whereas the hepatopancreas and plasma have no TGase activity. A 3199 bp cDNA encoding a TGase was isolated from a crayfish haemocyte cDNA library. The deduced protein comprises 766 amino acid residues and has a calculated molecular mass of between 85 930 and 86 034 kDa due to four amino acid vari ations. This gene is expressed as a single 4.9 kb transcript exclusively in the haemocytes and at very low levels in muscle and the hepatopancreas. Se quence comparison shows that this TGase has significant similarities to oth er TGases from invertebrates and mammals. (C) 2001 Academic Press.