Vander Jagt D L, Hunsaker L A, Campos N M
Department of Biochemistry, University of New Mexico, School of Medicine, Albuquerque 87131.
Biochem Pharmacol. 1987 Oct 1;36(19):3285-91. doi: 10.1016/0006-2952(87)90646-0.
An aminopeptidase and four hemoglobin-degrading acid proteases have been isolated from cloned strains of chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum. Amino-peptidases from both strains showed similar properties including molecular weights of 63,000 and non-competitive inhibition by chloroquine; Ki = 535 and 410 microM for enzymes from the sensitive and resistant strains respectively. The acid proteases from the chloroquine-sensitive strain included a low molecular weight enzyme in the soluble fraction (protease S), an enzyme weakly associated with membrane (protease M2), and two enzymes strongly associated with membrane (proteases M3 and M4). The acid proteases from the chloroquine-resistant strain included protease S, protease M2, a second enzyme weakly associated with membrane (protease M1), and protease M3. All of the acid proteases were inhibited by ferriprotoporphyrin IX and by the chloroquine-ferriprotoporphyrin IX complex, I50 = 5-25 microM. The data were consistent with a model for chloroquine action wherein chloroquine acts to divert ferriprotoporphyrin IX from sequestration into malarial pigment, leaving ferriprotoporphyrin IX (or its chloroquine complex) to interfere with digestion of host cytosol by inhibiting hemoglobin-degrading proteases. However, the similarities among the proteases from chloroquine-sensitive and chloroquine-resistant strains of parasites suggest that chloroquine resistance does not result from changes in parasite proteases.
已从对氯喹敏感和对氯喹耐药的恶性疟原虫克隆株中分离出一种氨肽酶和四种降解血红蛋白的酸性蛋白酶。两种菌株的氨肽酶表现出相似的特性，包括分子量为63,000以及对氯喹的非竞争性抑制；敏感株和耐药株酶的抑制常数（Ki）分别为535和410微摩尔。对氯喹敏感菌株的酸性蛋白酶包括可溶性部分中的一种低分子量酶（蛋白酶S）、一种与膜弱相关的酶（蛋白酶M2）以及两种与膜强相关的酶（蛋白酶M3和M4）。对氯喹耐药菌株的酸性蛋白酶包括蛋白酶S、蛋白酶M2、另一种与膜弱相关的酶（蛋白酶M1）和蛋白酶M3。所有酸性蛋白酶均被高铁原卟啉IX和氯喹 - 高铁原卟啉IX复合物抑制，半数抑制浓度（I50）为5 - 25微摩尔。这些数据与氯喹作用模型一致，即氯喹的作用是使高铁原卟啉IX从被隔离形成疟色素中转移出来，使高铁原卟啉IX（或其氯喹复合物）通过抑制降解血红蛋白的蛋白酶来干扰宿主细胞质的消化。然而，寄生虫对氯喹敏感和耐药菌株的蛋白酶之间的相似性表明，氯喹耐药性并非由寄生虫蛋白酶的变化引起。
