Regulation and physiological role of cyanide-resistant oxidases in fungi and plants

Data on the induction and regulation of cyanide-resistant oxidases in eucar yotic microorganisms and higher plants are reviewed. Expression of an alter native oxidase gene can be caused by a decrease in energy charge in cells. Some evidence exists suggesting that cAMP and Ca2+ act as intracellular sig nals inducing the expression of the alternative oxidase genes. Under certai n conditions cells produce alternative oxidases which remain in an inactive state. Activation of the alternative pathway of cell respiration is usuall y observed when electron transport via cytochromes is inhibited. The physio logical role of the alternative oxidase is discussed.