A new function for mitochondria

Mitochondria are synonymous with energy production. But new evidence from Marisol Quintero, Sergio Colombo, Andrew Godfrey, and Salvador Moncada (University College London, UK) suggests that mitochondria in the vascular endothelium are more signaling organelles than power plants.

Although vascular endothelial cells are crowded with mitochondria, these organelles are not the main ATP generators. Vascular endothelial cells are instead highly glycolytic, despite their close proximity to O₂ in the blood. Moncada's group had previously found that nitric oxide (NO), which is abundant in vascular endothelial cells, efficiently competes with O₂ for the binding to the cytochrome c oxidase, the terminal enzyme in the mitochondrial respiratory chain.

In the new report, the authors show that, at relatively low O₂ concentrations, this competition diverts O₂ away from the mitochondria into...