A Novel Mercaptopyruvate Sulfurtransferase Thioredoxin-Dependent Redox-Sensing Molecular Switch: A Mechanism for the Maintenance of Cellular Redox Equilibrium

Noriyuki      Nagahara

doi:10.2174/138955708784534409

Abstract

An intermolecular disulfide bond serves as a thioredoxin-dependent redox-sensing switch for the regulation of the enzymatic activity of 3-mercaptopyruvate sulfurtransferase (MST, EC.2.8.1.2). A cysteine residue on the surface of each subunit was oxidized to form an intersubunit disulfide bond so as to decrease MST activity, and thioredoxin-specific conversion of a dimer to a monomer increased MST activity. Further, a low redox potential sulfenate was reversibly formed at a catalytic site cysteine so as to inhibit MST, and thioredoxin-dependent reduction of the sulfenate restored the MST activity. Concludingly, MST partly contributes to the maintenance of cellular redox homeostasis via exerting control over cysteine catabolism.

Keywords: Atmospheric oxygen, antioxidative stress, intermolecular disulfide bond, mercaptolactate-cysteine disulfiduria, mercaptopyruvate sulfurtransferase, molecular evolution, redox-sensing switch, thioredoxin