A MALARIAL CYSTEINE PROTEINASE IS NECESSARY FOR HEMOGLOBIN DEGRADATION BY PLASMODIUM-FALCIPARUM
A MALARIAL CYSTEINE PROTEINASE IS NECESSARY FOR HEMOGLOBIN DEGRADATION BY PLASMODIUM-FALCIPARUM
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DOI：
10.1172/jci113766
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发表时间：
1988-11-01
影响因子：
15.9
通讯作者：
LEECH, JH
中科院分区：
文献类型：
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作者：
ROSENTHAL, PJ;MCKERROW, JH;LEECH, JH
为了获得蛋白质合成所需的游离氨基酸，滋养体阶段的疟疾寄生虫以宿主红细胞的细胞质为食，并在酸性食物液泡中降解血红蛋白。食物液泡似乎类似于哺乳动物细胞的次级溶酶体。为了确定血红蛋白降解的酶机制，我们将滋养体感染的红细胞与不同类型的蛋白酶的多肽抑制剂孵育。半胱氨酸蛋白酶的两种多肽抑制剂亮肽素和L-transepoxy-succinyl-leucyl-amido-(4-guanidino)-butane(E-)抑制了珠蛋白的蛋白降解，并导致寄生的食物空泡中劣质红细胞细胞质的积累，这表明食物空泡中的半胱氨酸蛋白酶是血红蛋白降解所必需的。对滋养体的蛋白酶分析表明，其半胱氨酸蛋白酶活性与食物液泡的最适pH相似，并具有溶酶体组织蛋白L的底物专一性。此外，还鉴定出一种滋养体阶段特异的MR 28,000蛋白水解酶，该酶可被亮胃素和E-抑制。我们得出结论，MR 28,000半胱氨酸蛋白酶在恶性疟原虫食物液泡内的血红蛋白降解中具有关键的，也许是限速的作用。这种酶的特定抑制剂可能为抗疟疾化疗提供新的手段。
To obtain free amino acids for protein synthesis, trophozoite stage malaria parasites feed on the cytoplasm of host erythrocytes and degrade hemoglobin within an acid food vacuole. The food vacuole appears to be analogous to the secondary lysosomes of mammalian cells. To determine the enzymatic mechanism of hemoglobin degradation, we incubated trophozoite-infected erythrocytes with peptide inhibitors of different classes of proteinases. Leupeptin and L-transepoxy-succinyl-leucyl-amido-(4-guanidino)-butane (E-64), two peptide inhibitors of cysteine proteinases, inhibited the proteolysis of globin and caused the accumulation of undergraded erythrocytes cytoplasm in parasite food vacuoles, suggesting that a food vacuole cysteine proteinase is necessary for hemoglobin degradation. Proteinase assays of trophozoites demonstrated cysteine proteinase activity with a pH optimum similar to that of the food vacuole and the substrate specificity of lysosomal cathepsin L. We also identified an Mr 28,000 proteinase that was trophozoite stage-specific and was inhibited by leupeptin and E-64. We conclude that the Mr 28,000 cysteine proteinase has a critical, perhaps rate-limiting role in hemoglobin degradation within the food vacuole of Plasmodium falciparum. Specific inhibitors of this enzyme might provide new means of antimalarial chemotherapy.