A high molecular weight proteinase inhibitor has been purified from the body fluid of sea crab (Portunus trituberculatus) using biospecific Zn^(2+) chelate affinity chromatography. The proteinase inhibitor inhibits the proteolytic activity of a variet...
A high molecular weight proteinase inhibitor has been purified from the body fluid of sea crab (Portunus trituberculatus) using biospecific Zn^(2+) chelate affinity chromatography. The proteinase inhibitor inhibits the proteolytic activity of a variety of endopeptidase such as trypsin, chymotrypsin and thermolysin. Like other vertebrate α-M, the sea crab α-macroglobulin (α-M) was composed of subunits of molecular weight 180 kDa as judged by polyacrylamide gel electrophoresis under reducing conditions. The apparent native molecular weight of the sea crab α-M determined by gel filtration was 360 kDa. Thermal fragmentation studies revealed that the monomer (180 kDa) was broken down into 95 kDa and 85 kDa fragments, respectively. On the basis of above results, it is concluded that the sea crab α-M is a dimer consisting of two weakly bound monomer,and the autolytic cleavage occurs easily by SDS and heat treatment.