Malate Oxidation, Rotenone-Resistance, and Alternative Path Activity in Plant Mitochondria Academic Article uri icon

abstract

  • The effect of cyanide and rotenone on malate (pH 6.8), malate plus glutamate (pH 7.8), citrate, alpha-ketoglutarate, and succinate oxidation by cauliflower (Brassica oleracea L.) bud, sweet potato (Ipomoea batatis L.) tuber, and spinach (Spinacia oleracea and Kalancho├ź daigremontiana leaf mitochondria was investigated. Cyanide inhibited all substrates equally with the exception of malate plus glutamate; in this case, inhibition of O(2) uptake was more severe due to an effect of cyanide on aspartate aminotransferase. Azide and antimycin A gave similar inhibitions with all substrates. Subsequent addition of NAD had no effect with any substrate. Providing that oxalacetate accumulation was prevented, rotenone inhibited all NAD-linked substrates equally and caused ADP:O ratios to decrease by one-third. Addition of succinate to mitochondria oxidizing malate stimulated oxygen uptake, but adding citrate and alpha-ketoglutarate did not. These results indicate that there is no direct link between malic enzyme and the rotenone- and cyanide-resistant respiratory pathways, and that there is no need to postulate separate compartmentation of malic enzyme and the other NAD-linked enzymes in the matrix.

publication date

  • October 1, 1982