Chapter 2

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

Noriyuki Nagahara

Abstract

3-Mercaptopyruvate sulfurtransferase (MST, EC.2.8.1.2) has two thioredoxin-dependent redox-sensing switches for the regulation of the enzymatic activity. One is an intermolecular disulfide bond formed between two subunits: 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. Another switch is a catalytic site cysteine, which reversibly forms a low redox potential sulfenate 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. This report is an updated version of the previous review [1] with small modifications.

Total Pages: 56-72 (17)

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