The proline metabolism intermediate Δ1-pyrroline-5-carboxylate directly inhibits the mitochondrial respiration in budding yeast

► P5C-mediated cell death is not due to classical P5C metabolism. ► Mitochondrial respiration is involved in the sensitivity of yeast cells to P5C. ► P5C directly inhibits the mitochondrial respiration. ► P5C induces the generation of superoxide anions from the mitochondria. ► P5C may regulate cell death via the inhibition of mitochondrial respiration.