Goldberg D E, Slater A F, Beavis R, Chait B, Cerami A, Henderson G B
Laboratory of Medical Biochemistry, Rockefeller University, New York, New York 10021.
J Exp Med. 1991 Apr 1;173(4):961-9. doi: 10.1084/jem.173.4.961.
Hemoglobin is an important nutrient source for intraerythrocytic malaria organisms. Its catabolism occurs in an acidic digestive vacuole. Our previous studies suggested that an aspartic protease plays a key role in the degradative process. We have now isolated this enzyme and defined its role in the hemoglobinolytic pathway. Laser desorption mass spectrometry was used to analyze the proteolytic action of the purified protease. The enzyme has a remarkably stringent specificity towards native hemoglobin, making a single cleavage between alpha 33Phe and 34Leu. This scission is in the hemoglobin hinge region, unraveling the molecule and exposing other sites for proteolysis. The protease is inhibited by pepstatin and has NH2-terminal homology to mammalian aspartic proteases. Isolated digestive vacuoles make a pepstatin-inhibitable cleavage identical to that of the purified enzyme. The pivotal role of this aspartic hemoglobinase in initiating hemoglobin degradation in the malaria parasite digestive vacuoles is demonstrated.
血红蛋白是红细胞内疟原虫的重要营养来源。其分解代谢发生在酸性消化泡中。我们之前的研究表明，一种天冬氨酸蛋白酶在降解过程中起关键作用。我们现已分离出这种酶，并确定了其在血红蛋白溶解途径中的作用。激光解吸质谱法用于分析纯化蛋白酶的蛋白水解作用。该酶对天然血红蛋白具有非常严格的特异性，在α33苯丙氨酸和34亮氨酸之间进行单一切割。这种切割发生在血红蛋白的铰链区，使分子解开并暴露出其他蛋白水解位点。该蛋白酶被胃蛋白酶抑制剂抑制，并且在氨基末端与哺乳动物天冬氨酸蛋白酶具有同源性。分离出的消化泡产生与纯化酶相同的胃蛋白酶抑制剂可抑制的切割。证明了这种天冬氨酸血红蛋白酶在疟原虫消化泡中启动血红蛋白降解的关键作用。
