Diaz F, Komuniecki R W
Department of Biology, University of Toledo, OH 43606.
Mol Biochem Parasitol. 1994 Oct;67(2):289-99. doi: 10.1016/0166-6851(94)00134-0.
The pyruvate dehydrogenase complex (PDC) has been purified to apparent homogeneity from 2 parasitic helminths exhibiting anaerobic mitochondrial metabolism, the equine nematode, Parascaris equorum, and the canine cestode, Dipylidium caninum. The P. equorum PDC yielded 7 major bands when separated by SDS-PAGE. The bands of 72, 55-53.5, 41 and 36 kDa corresponded to E2, E3, E1 alpha and E1 beta, respectively. The complex also contained additional unidentified proteins of 43 and 45 kDa. Incubation of the complex with [2-14C]pyruvate resulted in the acetylation of only E2. These results suggest that the P. equorum PDC lacks protein X and exhibits an altered subunit composition, as has been described previously for the PDC of the related nematode, Ascaris suum. In contrast, the D. caninum PDC yielded only four major bands after SDS-PAGE of 59, 58, 39 and 34 kDa, which corresponded to E3, E2, E1 alpha and E1 beta, respectively. Incubation of the D. caninum complex with [2-14C]pyruvate resulted in the acetylation of E2 and a second protein which comigrated with E3, suggesting that the D. caninum complex contained protein X and had a subunit composition similar to PDCs from other eukaryotic organisms. Both helminth complexes appeared less sensitive to inhibition by elevated NADH/NAD+ ratios than complexes isolated from aerobic organisms, as would be predicted for PDCs from organisms exploiting microaerobic habitats. These results suggest that although these helminths have similar anaerobic mitochondrial pathways, they contain significantly different PDCs.
丙酮酸脱氢酶复合体（PDC）已从两种呈现厌氧线粒体代谢的寄生蠕虫中纯化至表观均一，这两种蠕虫分别是马线虫，马副蛔虫，以及犬绦虫，犬复孔绦虫。马副蛔虫PDC经SDS-PAGE分离后产生7条主要条带。72 kDa、55 - 53.5 kDa、41 kDa和36 kDa的条带分别对应E2、E3、E1α和E1β。该复合体还含有另外两种未鉴定的43 kDa和45 kDa的蛋白质。该复合体与[2-¹⁴C]丙酮酸孵育后仅导致E2发生乙酰化。这些结果表明，马副蛔虫PDC缺乏蛋白X且呈现出改变的亚基组成，正如先前对相关线虫猪蛔虫的PDC所描述的那样。相比之下，犬复孔绦虫PDC经SDS-PAGE后仅产生4条主要条带，分别为59 kDa、58 kDa、39 kDa和34 kDa，它们分别对应E3、E2、E1α和E1β。犬复孔绦虫复合体与[2-¹⁴C]丙酮酸孵育后导致E2和另一种与E3迁移率相同的蛋白质发生乙酰化，这表明犬复孔绦虫复合体含有蛋白X且具有与其他真核生物的PDC相似的亚基组成。与从需氧生物中分离的复合体相比，这两种蠕虫的复合体对NADH/NAD⁺比率升高的抑制作用似乎不太敏感，这正如利用微需氧生境的生物的PDC所预期的那样。这些结果表明，尽管这些蠕虫具有相似的厌氧线粒体途径，但它们含有的PDC却有显著差异。
