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