Saruta F, Kuramochi T, Nakamura K, Takamiya S, Yu Y, Aoki T, Sekimizu K, Kojima S, Kita K
Department of Parasitology, University of Tokyo, Japan.
J Biol Chem. 1995 Jan 13;270(2):928-32. doi: 10.1074/jbc.270.2.928.
Complex II from mitochondria of the adult parasitic nematode, Ascaris suum, exhibits high fumarate reductase activity and plays a key role in the anaerobic electron transport observed in these organelles. In contrast, mitochondria isolated from free living second stage larvae (L2) of A. suum show much lower fumarate reductase activity than those from adults, whereas succinate dehydrogenase activities of mitochondria in both stages are comparable. In the present study, biochemical and antigenic properties of the partially purified enzymes from both larval and adult mitochondria were compared. Larval complex II eluted from the DEAE-Cellulofine column chromatography at a lower salt concentration than adult enzyme, whereas the apparent molecular size of both enzyme complexes estimated by gel permeation column chromatography was the same. The fumarate reductase activity of larval complex II was less than 3% of that of adult enzyme, and the Km values for substrates were significantly different between the two complexes. The flavoprotein subunit of larval complex II could be distinguished from that of adult complex II by two-dimensional gel electrophoresis and peptide mapping. The antibody against the smallest subunit (small subunit of cytochrome b558) of the adult enzyme did not cross-react with that of the larval enzyme. These results suggest that larval complex II differs from adult enzyme and is more similar to aerobic mammalian enzymes with low fumarate reductase activity. This is the first direct indication of the two different stage-specific forms of mitochondrial complex II.
成年寄生线虫猪蛔虫线粒体中的复合物II具有较高的延胡索酸还原酶活性，在这些细胞器中观察到的厌氧电子传递中起关键作用。相比之下，从猪蛔虫自由生活的第二阶段幼虫（L2）中分离出的线粒体显示出的延胡索酸还原酶活性比成虫的低得多，而两个阶段线粒体的琥珀酸脱氢酶活性相当。在本研究中，比较了幼虫和成虫线粒体中部分纯化酶的生化和抗原特性。幼虫复合物II从DEAE-纤维素柱层析中洗脱时的盐浓度低于成虫酶，而通过凝胶渗透柱层析估计的两种酶复合物的表观分子大小相同。幼虫复合物II的延胡索酸还原酶活性不到成虫酶的3%，并且两种复合物底物的Km值有显著差异。幼虫复合物II的黄素蛋白亚基可通过二维凝胶电泳和肽图与成虫复合物II的区分开来。针对成虫酶最小亚基（细胞色素b558的小亚基）的抗体与幼虫酶的抗体不发生交叉反应。这些结果表明，幼虫复合物II与成虫酶不同，并且更类似于具有低延胡索酸还原酶活性的需氧哺乳动物酶。这是线粒体复合物II两种不同阶段特异性形式的首个直接证据。
