Roles for two aminopeptidases in vacuolar hemoglobin catabolism in Plasmodium falciparum
Roles for two aminopeptidases in vacuolar hemoglobin catabolism in Plasmodium falciparum
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DOI：
10.1074/jbc.m703643200
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发表时间：
2007-12-07
影响因子：
4.8
通讯作者：
Klemba, Michael
中科院分区：
文献类型：
--
作者：
Dalal, Seema;Klemba, Michael
在其生命周期的红血球阶段，人类疟疾寄生虫恶性疟原虫在一个酸性细胞器--食物液泡中分解大量宿主细胞血红蛋白。目前一种珠蛋白来源的寡肽分解代谢的模型是将多肽运输出食物液泡，然后由胞浆氨基肽酶将其水解为氨基酸。为了验证这一模型，我们研究了四种寄生虫氨基肽酶在红细胞周期中的作用。标记氨基肽酶的定位，结合对丰富的食物液泡的生化分析，揭示了食物液泡和细胞质中存在氨基酸生成途径。根据定位数据和体外分析，我们提出了一种质原酶，氨基肽酶P，在液泡和胞浆中含有脯氨酸多肽的分解代谢中的特殊作用。我们确定了四种氨基肽酶中的三种(包括两种食物液泡酶)对寄生虫有效增殖的明显要求。为了深入了解氨基肽酶抑制对寄生虫发育的影响，我们检测了寄生虫培养液中氨基酸的存在对氨基肽酶抑制剂Bestatin毒性的影响。当20个氨基酸中的19个从培养液中移除时，Best atin阻止寄生虫复制的能力仅受到轻微影响，表明外源氨基酸不能补偿氨基肽酶活性的损失。总之，这些结果支持氨基肽酶抑制剂作为针对疟疾的新型化疗药物的开发。
During the erythrocytic stage of its life cycle, the human malaria parasite Plasmodium falciparum catabolizes large quantities of host-cell hemoglobin in an acidic organelle, the food vacuole. A current model for the catabolism of globin-derived oligopeptides invokes peptide transport out of the food vacuole followed by hydrolysis to amino acids by cytosolic aminopeptidases. To test this model, we have examined the roles of four parasite aminopeptidases during the erythrocytic cycle. Localization of tagged aminopeptidases, coupled with biochemical analysis of enriched food vacuoles, revealed the presence of amino acid-generating pathways in the food vacuole as well as the cytosol. Based on the localization data and in vitro assays, we propose a specific role for one of the plasmodial enzymes, aminopeptidase P, in the catabolism of proline-containing peptides in both the vacuole and the cytosol. We establish an apparent requirement for three of the four aminopeptidases ( including the two food vacuole enzymes) for efficient parasite proliferation. To gain insight into the impact of aminopeptidase inhibition on parasite development, we examined the effect of the presence of amino acids in the culture medium of the parasite on the toxicity of the aminopeptidase inhibitor bestatin. The ability of bestatin to block parasite replication was only slightly affected when 19 of 20 amino acids were withdrawn from the medium, indicating that exogenous amino acids cannot compensate for the loss of aminopeptidase activity. Together, these results support the development of aminopeptidase inhibitors as novel chemotherapeutics directed against malaria.