꽃게(Portunus trituberculatus) 체액을 $Zn^{2+}$ -chelate affinity column을 이용하여 분리 정제하였다. 그 결과 척추동물의 경우와는 달리 affinity gel의 재생과정($Zn^{2+}$ 이온제거)인 50mM EDTA(ethylene diaminetetraacetic acid) 분획에서 ${alpha}-macroglobulin({alpha}-M)$이 분리되였다. 꽃게의 ${alpha}-macroglobulin$은 trypsin, chymotrypsin, thermolysin의 활성을 억제하였으나, 사람의 ${alpha}_{2}-macroglobulin$과는 달리 subtilisin과 cathepsin C 등의 활성은 억제하지 못하였다. 또한 고등동물의 경우와 달리 trypsin 보다는 thermolysin과의 친화력이 높았다. 꽃게 ${alpha}-M$은 monomer의 분자량이 180 kDa인 dimer의 행태로 존재하며 상기 monomer는 열과 detergent(SDS)에 의해서 분자량 95 kDa 및 85 kDa의 polypeptide로 분리되었다.
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 ${alpha}-M$, the sea crab ${alpha}-macroglobulin$ $({alpha}-M)$ 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 ${alpha}-M$ 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 ${alpha}-M$ is a dimer consisting of two weakly bound monomer,and the autolytic cleavage occurs easily by SDS and heat treatment.
