Sulfide oxidation coupled to ATP synthesis in chicken liver mitochondria

Abstract

Chicken liver mitochondria consumed O 2 at an accelerated rate when supplied with low concentrations of hydrogen sulfide. Maximum respiration occurred in 10 μM sulfide, and continued more slowly up to concentrations as high as 60 μM. Sulfide oxidation was coupled to adenosine triphosphate (ATP) synthesis, as shown by firefly luciferase luminescence and by measurement of the mitochondrial membrane electrochemical gradient. Synthesis of ATP required low, steady-state concentrations of sulfide (<5 μM), which were maintained by use of a syringe pump. The ratio of consumed O 2 to sulfide changed at low sulfide and O 2 concentrations, indicating alternative metabolic reactions and products. In low concentrations of sulfide, presumably most similar to physiological, the O 2/sulfide ratio was 0.75. This is the first report of sulfide oxidation linked to ATP synthesis in any organism not specifically adapted to a sulfide-rich environment. We suggest that this may be a widespread mitochondrial trait, and that it is consistent with the hypothesis that mitochondria originated from sulfide-oxidizing symbionts.