Generating Disulfides Enzymatically: Reaction Products and Electron Acceptors of the Endoplasmic Reticulum Thiol Oxidase Ero1p

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 103; no. 2; pp. 299 - 304
• Main Authors: Gross, Einav, Sevier, Carolyn S., Heldman, Nimrod, Vitu, Elvira, Bentzur, Moran, Kaiser, Chris A., Thorpe, Colin, Fass, Deborah
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 10-01-2006; National Acad Sciences
• Subjects: Binding Sites; Biological Sciences; Catalysis; Cells; Disulfides; Disulfides - metabolism; Electron transfer; Electron Transport; Electrons; Endoplasmic Reticulum - enzymology; Enzymes; Eukaryotes; Flavins - pharmacology; Glycoproteins - chemistry; Glycoproteins - genetics; Glycoproteins - metabolism; Hydrogen; Hydrogen Peroxide - pharmacology; Models, Molecular; Oxidases; Oxidation; Oxidation-Reduction - drug effects; Oxidoreductases Acting on Sulfur Group Donors - chemistry; Oxidoreductases Acting on Sulfur Group Donors - genetics; Oxidoreductases Acting on Sulfur Group Donors - metabolism; Oxygen; Oxygen consumption; Peroxides; Protein Structure, Tertiary; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Spectrum Analysis; Substrate Specificity; Sulfhydryl Compounds - metabolism; Thiols; Titrimetry; Yeast
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0506448103

Ero1p is a key enzyme in the disulfide bond formation pathway in eukaryotic cells in both aerobic and anaerobic environments. It was previously demonstrated that Ero1p can transfer electrons from thiol substrates to molecular oxygen. However, the fate of electrons under anaerobic conditions and the final fate of electrons under aerobic conditions remained obscure. To address these fundamental issues in the Ero1p mechanism, we studied the transfer of electrons from recombinant yeast Ero1p to various electron acceptors. Under aerobic conditions, reduction of molecular oxygen by Ero1p yielded stoichiometric hydrogen peroxide. Remarkably, we found that reduced Ero1p can transfer electrons to a variety of small and macromolecular electron acceptors in addition to molecular oxygen. In particular, Ero1p can catalyze reduction of exogenous FAD in solution. Free FAD is not required for the catalysis of dithiol oxidation by Ero1p, but it is sufficient to drive disulfide bond formation under anaerobic conditions. These findings provide insight into mechanisms for regenerating oxidized Ero1p and maintaining disulfide bond formation under anaerobic conditions in the endoplasmic reticulum.