Studies on human plasma alpha 2-macroglobulin-enzyme interactions. Evidence for proteolytic modification of the subunit chain structure.
Studies on human plasma alpha 2-macroglobulin-enzyme interactions. Evidence for proteolytic modification of the subunit chain structure.
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DOI：
10.1084/jem.138.3.508
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发表时间：
1973-09-01
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影响因子：
--
通讯作者：
Harpel PC
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作者：
Harpel PC
人血浆α-2-巨球蛋白是一种在止血和炎症反应中发挥作用的循环蛋白酶的抑制物，但其与这些酶相互作用的生化性质尚未很好地确定。这项研究发现，α2-巨球蛋白由185,000个分子量的亚单位链组成，在含有十二烷基硫酸钠的聚丙烯酰胺凝胶中进行电泳法分析。与α2完全结合的胰酶、凝血酶、纤溶酶和血浆激肽释放酶攻击亚基链上的一个区域，产生一个分子量为85,000的单一衍生物，表明水解发生在母链的中心或附近。在与纤溶酶原激活剂尿激活剂孵育的血浆中的α-2-巨球蛋白制剂中也发现了蛋白水解物。由于不能结合胰酶的酸变性α2-巨球蛋白被广泛降解，因此，能够结合酶的α2-巨球蛋白似乎是限制胰酶水解和将浓度依赖的衍生链增加限制在孵育1分钟所必需的。α-2-巨球蛋白与凝乳酶的相互作用产生了三条衍生链，表明前体链中至少存在两个凝乳酶敏感区。α-2-巨球蛋白-酶混合物的还原需要鉴定衍生亚单位链，以确定这些裂解产物通过二硫键与亲本分子共价连接。因此，α2-顶球蛋白作为循环蛋白酶的底物，这一发现也可能与其他血浆酶抑制剂的作用机制有关。
Human plasma α2-macroglobulin is an inhibitor of circulating proteases that function in hemostatic and inflammatory reactions but the biochemical nature of its interaction with these enzymes is not well defined. This investigation has found that α2-macroglobulin is comprised of subunit chains of 185,000 molecular weight as analyzed by electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate. Trypsin, thrombin, plasmin, and plasma kallikrein in amounts completely bound to α2-macroglobulin attacked one region in the subunit chain producing a single derivative with a molecular weight of 85,000 indicating that hydrolysis occurred at or near the center of the parent chain. The proteolytic derivative was also identified in an α2-macroglobulin preparation from plasma incubated with the plasminogen activator, urokinase. α2-macroglobulin functionally capable of binding enzyme appeared to be required both for limiting tryptic hydrolysis and for confining the concentration dependent increase in the derivative chain to the 1st min of incubation since acid-denatured α2-macroglobulin that failed to bind trypsin was extensively degraded. Three derivative chains resulted from the interaction of α2-macroglobulin with chymotrypsin demonstrating the presence of at least two chymotrypsin susceptible regions in the precursor chain. Reduction of the α2-macroglobulin-enzyme mixture was required for the identification of the derivative subunit chains establishing that these cleavage products were covalently linked to the parent molecule by disulfide bridges. Thus, α2-inacroglobulin acts as a substrate for circulating proteases, a finding which may also pertain to the mechanism of action of other plasma enzyme inhibitors.