Suzuki Takashi, Nihei Coh-ichi, Yabu Yoshisada, Hashimoto Tetsuo, Suzuki Mitsuko, Yoshida Ayako, Nagai Kazuo, Hosokawa Tomoyoshi, Minagawa Nobuko, Suzuki Shuichi, Kita Kiyoshi, Ohta Nobuo
Department of Molecular Parasitology, Nagoya City University, Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
Parasitol Int. 2004 Sep;53(3):235-45. doi: 10.1016/j.parint.2004.02.001.
Trypanosoma vivax causes nagana disease in cattle. Since T. vivax is transmitted not only by tsetse flies but also by other biting flies (non-cyclic transmission), the parasite has been distributed to and has had a significant economic impact on wide geographical areas, including Africa and South America. Our previous study on Trypanosoma brucei brucei showed that the trypanosome alternative oxidase (TAO, TbAOX) is a promising target of chemotherapy. For this reason, we also have cloned the T vivax AOX (TvAOX) gene and characterized the recombinant enzyme. The deduced amino acid sequence (328 a.a.) of TvAOX shares 76% identity with TbAOX and contains the diiron-coordination motifs (-E-, -EXXH-) that are conserved among AOXs. The Km of recombinant TvAOX (rTvAOX) expressed in Escherichia coli for ubiquinol (87.0 +/- 0.54 microM) was significantly lower than the value for recombinant TbAOX (rTbAOX) (714 +/- 4.5 microM). Ascofuranone, the most potent inhibitor of TbAOX, was a competitive inhibitor of rTvAOX with a Ki value (0.40 +/- 0.00 nM) significantly lower than that for rTbAOX (1.29 +/- 0.00 nM). The non-cyclic transmission ability of T. vivax and the in vivo chemotherapeutic efficacy of ascofuranone against T. vivax and T. b. brucei infection are discussed in terms of these Km and Ki values.
活泼锥虫可引发牛的那加那病。由于活泼锥虫不仅通过采采蝇传播，还可通过其他叮咬类苍蝇传播（非循环传播），该寄生虫已传播至包括非洲和南美洲在内的广大地理区域，并对这些地区造成了重大经济影响。我们之前对布氏布氏锥虫的研究表明，锥虫交替氧化酶（TAO，TbAOX）是一个很有前景的化疗靶点。因此，我们还克隆了活泼锥虫AOX（TvAOX）基因，并对重组酶进行了表征。TvAOX推导的氨基酸序列（328个氨基酸）与TbAOX的序列一致性为76%，并包含在AOX中保守的双铁配位基序（-E-，-EXXH-）。在大肠杆菌中表达的重组TvAOX（rTvAOX）对泛醇的米氏常数（Km）（87.0±0.54μM）显著低于重组TbAOX（rTbAOX）的值（714±4.5μM）。Ascofuranone是TbAOX最有效的抑制剂，它是rTvAOX的竞争性抑制剂，其抑制常数（Ki）值（0.40±0.00 nM）显著低于rTbAOX的（1.29±0.00 nM）。本文根据这些Km和Ki值讨论了活泼锥虫的非循环传播能力以及Ascofuranone对活泼锥虫和布氏布氏锥虫感染的体内化疗效果。
