Amytal mitochondrial

The movement of electrons through the electron carrying proteins of the inner mitochondrial membrane is shown in Figure 15.9. Also shown are inhibitors of electron movement at their point of action and the sites where artificial electron acceptors can accept electrons from the electron transport system. Specific inhibitors shown in Figure 15.9 are rotenone, amytal, antimycin A, cyanide, azide, and carbon monoxide. The artificial electron acceptors are methylene blue, phenazine methosulfate, 2,6-indophenol, tetramethyl-p-phenylene diamine, and ferricyanide. 

Canvin and Woo (1979) reported that under certain conditions Antimycin A (mitochondrial ATP site II inhibitor) was more effective in enhancing nitrite accumulation (75% of anaerobic control) by leaf discs than either amytal or rotenone (ATP site I inhibitors). In plant mitochondria, the malate dehydrogenase located on the outside of the inner membrane is capable of utilizing external NADH. They infer that in leaves under dark aerobic conditions, the mitochondria effectively compete with nitrate reductase for cytoplasmic NADH. Confirmation of this competition was afforded by a reconstituted system consisting of mitochondria, nitrate reductase, nitrate and NADH or NAD, malate, and malate dehydrogenase (Reed and Hageman, 1977). Nitrite production under aerobic conditions was 10% that observed under anaerobiosis. 

Rotenone is used experimentally as an inhibitor of mitochondrial respiration. It has little effect on the mitochondrial oxidation of succinate, but it powerfully inhibits all oxidations which operate via NADH dehydrogenase. The site of inhiUtion by rotenone has been located on the oxygen side of the nonheme iron of NADH dehydrogenase (see Respiratory chain). Piericidin and amytal appear to act at or very close to the same site. [W. W. Wainio The Mammalum Mitochondrial Respiratory Chain (Academic Press, 1970) T.P. Singer M. Gutman Adv. Enzmol. 34 (1971) 79-153 J.B.Harbome, T.J.Mabry H.Mabry eds. TTie Flavonoids (Chapman Hall, 1975)] rRNA ribosomal RNA (see Ribosomes). 

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