Köhler P, Bachmann R
Mol Biochem Parasitol. 1980 Apr;1(2):75-90. doi: 10.1016/0166-6851(80)90002-x.
In Ascaris muscle mitochondria the major respiratory chain-linked phosphorylation activity is accomplished by a NADH-linked reduction of fumarate to succinate. Oxygen can also be employed as a terminal electron acceptor via a cyanide- and salicyl-hydroxamate-resistant terminal oxidase. As in fumarate-dependent electron transport this process appears to be coupled to energy conservation at phosphorylation site I. The branchpoint from which electrons are taken from the main respiratory chain to either the alternative oxidase or fumarate reductase is likely to be on the oxygen side of the NADH dehydrogenase segment. Malate and succinate are the only substrates which appreciably support respiration in the mitochondrion of the nematode. Regardless of the presence or absence of oxygen malate is utilized by an oxidation-reduction reaction resulting in the formation of pyruvate, acetate, succinate, propionate and CO2. In addition, aerobically, hydrogen peroxide is formed as the product of oxygen reduction. Succinate accumulation was found to be significantly higher in the anaerobic as compared to the aerobic incubation mixtures. This effect was accompanied by an increase in anaerobic malate consumption. ATP generation and the formation of pyruvate, acetate and propionate were found to be similar in the presence and absence of oxygen. In malate-supported respiration of intact Ascaris mitochondria reducing equivalents (NADH) are produced exclusively through pyruvate and acetate formation. These enzymatic reactions are functionally coupled to the electron transport-linked reductions of fumarate to succinate and oxygen to hydrogen peroxide, respectively. In accordance with the position of the redox potentials of the fumarate/succinate and O2/H2O2 couples, anaerobic and aerobic respiration was found to be associated with relatively low energy conservation efficiencies. Thus one molecule of ATP was conserved per 2e- transferred to fumarate or oxygen, respectively. No evidence could be obtained for a significant activity of energy conservation sites II and III and electron transfer through the alternative oxidase pathway was shown not to be coupled to phosphorylation.
在蛔虫肌肉线粒体中，主要的呼吸链偶联磷酸化活性是通过NADH将延胡索酸还原为琥珀酸来实现的。氧气也可通过一种抗氰化物和水杨基异羟肟酸的末端氧化酶作为末端电子受体。与依赖延胡索酸的电子传递一样，这个过程似乎在磷酸化位点I与能量守恒相偶联。电子从主要呼吸链转移到交替氧化酶或延胡索酸还原酶的分支点可能位于NADH脱氢酶片段的氧气一侧。苹果酸和琥珀酸是仅有的能显著支持线虫线粒体呼吸的底物。无论有无氧气，苹果酸都通过氧化还原反应被利用，生成丙酮酸、乙酸、琥珀酸、丙酸和二氧化碳。此外，在有氧条件下，氧气还原会生成过氧化氢。与有氧孵育混合物相比，在厌氧条件下琥珀酸的积累显著更高。这种效应伴随着厌氧条件下苹果酸消耗的增加。在有无氧气的情况下，ATP的生成以及丙酮酸、乙酸和丙酸的形成情况相似。在完整蛔虫线粒体的苹果酸支持的呼吸中，还原当量（NADH）仅通过丙酮酸和乙酸的形成产生。这些酶促反应分别在功能上与电子传递偶联的延胡索酸还原为琥珀酸以及氧气还原为过氧化氢相偶联。根据延胡索酸/琥珀酸和O2/H2O2电对的氧化还原电位的位置，发现厌氧呼吸和好氧呼吸的能量守恒效率相对较低。因此，每向延胡索酸或氧气转移2个电子，分别会守恒一分子ATP。没有证据表明存在显著的能量守恒位点II和III的活性，并且通过交替氧化酶途径的电子传递未显示与磷酸化相偶联。
