Department of Biology and Molecular Biology Institute, University of California, Los Angeles, California 90024.
Plant Physiol. 1978 Aug;62(2):243-8. doi: 10.1104/pp.62.2.243.
The respiration of fresh sweet potato (Ipomoea batatas) slices is resistant to, and often stimulated by, cyanide and antimycin A. m-Chlorobenzhydroxamic acid (CLAM), a selective inhibitor of the alternate path, inhibits respiration in the presence of cyanide and has a limited inhibitory effect in the presence of antimycin A. Thus, a partial bypass of the antimycinsensitive site is indicated. Respiration rises 2-fold at best with slice aging, the increment being cytochrome-mediated. The cyanide-resistant pathway contributes neither to coupled fresh slice respiration nor to the induced respiration in the absence of inhibitors of the cytochrome path. In the presence of uncoupler, however, the alternate path is engaged both in fresh and aged slices. V(cyt), the maximal capacity of the cytochrome path, remains essentially the same with slice aging, whereas V(alt) decreases from 20 to 60 per cent. The induced respiration is readily accommodated by the potential cytochrome path capacity of fresh slices, which is realized on aging. Accordingly, there is no need to invoke mitochondrial proliferation in explanation of the development of the induced respiration. The engagement of the alternate path in response to uncoupler reflects substrate mobilization to a degree that substrate oxidation exceeds the electron transport capacity of the cytochrome path.Fresh slices do not utilize exogenous substrates, whereas aged slices do so readily. Cerulenin, a specific inhibitor of fatty acid synthesis, prevents the development of the induced respiration as well as the capacity to oxidize exogenous substrates. It is suggested that lipid, and ultimately membrane, biosynthesis is central to the development of the induced respiration and the ability to use exogenous substrates, much as in potato.
新鲜番薯（Ipomoea batatas）切片的呼吸作用对氰化物和抗霉素 A 有抗性，且通常会受到刺激。m-氯苯羟肟酸（CLAM）是交替途径的选择性抑制剂，它在氰化物存在的情况下抑制呼吸作用，并且在抗霉素 A 存在的情况下具有有限的抑制作用。因此，表明存在抗霉素 A 敏感部位的部分旁路。随着切片老化，呼吸作用最多增加 2 倍，增量是细胞色素介导的。氰化物抗性途径既不参与偶联新鲜切片呼吸作用，也不参与无细胞色素途径抑制剂时的诱导呼吸作用。然而，在解偶联剂存在的情况下，交替途径在新鲜和老化切片中都被激活。V(cyt)，即细胞色素途径的最大容量，随着切片老化基本保持不变，而 V(alt)则从 20%下降到 60%。诱导呼吸作用很容易被新鲜切片的潜在细胞色素途径容量所适应，这种容量在老化时实现。因此，没有必要援引线粒体增殖来解释诱导呼吸作用的发展。在解偶联剂的作用下，交替途径的参与反映了底物动员的程度，以至于底物氧化超过了细胞色素途径的电子传递能力。新鲜切片不利用外源底物，而老化切片则很容易利用。培西霉素是脂肪酸合成的特异性抑制剂，它既可以防止诱导呼吸作用的发展，也可以防止氧化外源底物的能力。有人认为，脂质，最终是膜，生物合成是诱导呼吸作用和利用外源底物能力发展的核心，就像在马铃薯中一样。
