Inactivation of complex I of the respiratory chain of maize mitochondria incubated in vitro by elevated temperature

The functional stability of the ‘external’ NADH dehydrogenase and complexes I–IV of the respiratory chain of maize mitochondria was studied during mitochondria incubation in vitro at elevated temperatures. The increase in the incubation temperature from 0°C to 37°C significantly changed the stability of the respiratory chain. At 27°C and higher, the rate of oxidation of NAD-depended substrates decreased drastically, which is related to inactivation of complex I. Complexes II, III and IV of the respiratory chain and the ‘external’ NADH dehydrogenase were functionally stable at elevated temperatures. Moreover, the possibility of electron transport during oxidation of NAD-dependent substrates, in particular malate, bypasses complex I using rotenon insensitive NADH dehydrogenase.