The Interaction between Exogenous NADH Oxidase and Succinate Oxidase in Jerusalem Artichoke (Helianthus tuberosus) Mitochondria

Most isolated plant mitochondria oxidize exogenous NADH viaan electron transport pathway which is resistant to piericidinA and coupled to the synthesis of two molecules of ATP. Resultspresented show that succinate can inhibit this oxidation ofadded NADH. The inhibition was most marked in the absence ofADP (state 4), less obvious in the presence of added ADP (state3), and absent in the presence of a weak acid uncoupling agent.The presence of malonate prevented the inhibition. The degreeof inhibition was dependent on the concentration of succinateand appeared to be non-competitive in nature. The inhibitionwas shown not to be the result of the reversed flow of electronsfrom succinate to NAD^$. The presence of external NADH appearednot to alter the rate of oxidation of succinate.