The kinetic basis of threshold effects observed in mitochondrial diseases: a systemic approach

Abstract

Threshold effects in the expression of metabolic diseases have often been observed in mitochondrial pathologies, i.e. the clinical demonstration of the disease appears only when the activity of a step has been reduced to a rather low level. We show experimentally that an inhibition of cytochrome c oxidase activity by cyanide, simulating a defect in this step, leads to a decrease in mitochondrial respiration which then exhibits a threshold behaviour similar to that observed in mitochondrial diseases. We discuss this behaviour in terms of metabolic control theory and construct a mathematical model simulating this behaviour.