Department of Cell Biology, The University of Brasília, Brasília, 70910-900, Brazil.
BMC Biochem. 2011 Aug 23;12:46. doi: 10.1186/1471-2091-12-46.
Pathogens depend on peptidase activities to accomplish many physiological processes, including interaction with their hosts, highlighting parasitic peptidases as potential drug targets. In this study, a major leucyl aminopeptidolytic activity was identified in Trypanosoma cruzi, the aetiological agent of Chagas disease.
The enzyme was isolated from epimastigote forms of the parasite by a two-step chromatographic procedure and associated with a single 330-kDa homohexameric protein as determined by sedimentation velocity and light scattering experiments. Peptide mass fingerprinting identified the enzyme as the predicted T. cruzi aminopeptidase EAN97960. Molecular and enzymatic analysis indicated that this leucyl aminopeptidase of T. cruzi (LAPTc) belongs to the peptidase family M17 or leucyl aminopeptidase family. LAPTc has a strong dependence on neutral pH, is mesophilic and retains its oligomeric form up to 80°C. Conversely, its recombinant form is thermophilic and requires alkaline pH.
LAPTc is a 330-kDa homohexameric metalloaminopeptidase expressed by all T. cruzi forms and mediates the major parasite leucyl aminopeptidolytic activity. Since biosynthetic pathways for essential amino acids, including leucine, are lacking in T. cruzi, LAPTc could have a function in nutritional supply.
病原体依赖肽酶活性来完成许多生理过程，包括与宿主的相互作用，这突显了寄生肽酶作为潜在药物靶点的重要性。在这项研究中，鉴定出了克氏锥虫（恰加斯病的病原体）中的一种主要亮氨酰氨肽酶活性。
该酶通过两步色谱程序从寄生虫的前鞭毛体形式中分离出来，并与单个 330 kDa 的同六聚体蛋白相关，这是通过沉降速度和光散射实验确定的。肽质量指纹图谱鉴定该酶为预测的克氏锥虫氨肽酶 EAN97960。分子和酶学分析表明，这种克氏锥虫亮氨酰氨肽酶（LAPTc）属于肽酶家族 M17 或亮氨酰氨肽酶家族。LAPTc 对中性 pH 有很强的依赖性，是嗜温的，并且在高达 80°C 的温度下保持其寡聚形式。相反，其重组形式是嗜热的，需要碱性 pH。
LAPTc 是一种 330 kDa 的同六聚体金属氨肽酶，由所有克氏锥虫形式表达，并介导主要寄生虫亮氨酰氨肽酶活性。由于克氏锥虫缺乏必需氨基酸（包括亮氨酸）的生物合成途径，因此 LAPTc 可能在营养供应中具有功能。
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