Synergistic effects of oxidoreductases (ERp46, ERp57, and P5) on oxygen consumption in the presence of PDI and constitutively active Ero1-α. (A) Schematic model of intermolecular electron flow among oxidoreductases. (B–E) Oxygen consumption was assayed in the presence of 10 mM GSH and 10 µM ERp46 (B), ERp57 (C), P5 (D), and ERp72 (E) with or without 5 µM PDI. Calc represents calculated data from individual consumption rates of the oxidoreductases. Mix represents actual consumption rates under conditions in which 10 µM of each oxidoreductase and 5 µM PDI were mixed in the presence of 10 mM GSH. (F) 10 µM P5 and 10 µM ERp57, without PDI, were mixed in the presence of 10 mM GSH. ROS, reactive oxygen species.