Acid-volatile selenium formation catalyzed by glutathione reductase

Area of Science:

• Biochemistry
• Enzymology
• Selenium Metabolism

Background:

• Glutathione reductase is a key enzyme in cellular redox homeostasis.
• Selenium is an essential trace element with complex biological roles.
• Understanding selenium detoxification pathways is important for human health.

Purpose of the Study:

• To investigate the role of glutathione reductase in the production of acid-volatile selenide (H2Se).
• To elucidate the mechanism of H2Se formation catalyzed by glutathione reductase.
• To identify factors affecting H2Se production and volatilization.

Main Methods:

• Enzymatic assays using purified yeast glutathione reductase.
• Anaerobic reaction systems with varying concentrations of glutathione, sodium selenite, and TPNH.
• Spectrophotometric monitoring of H2Se production.
• Inhibition studies using arsenite and bovine serum albumin.

Main Results:

• Glutathione reductase significantly catalyzed H2Se production in an anaerobic system.
• H2Se production was proportional to glutathione reductase concentration and optimal at pH 7.
• Nonenzymic H2Se production was observed in the absence of the enzyme and TPNH.
• Arsenite and bovine serum albumin inhibited Se volatilization, suggesting interaction with the selenide product.
• The selenotrisulfide derivative of glutathione (GSSeSG) was a key intermediate, readily converted to H2Se.

Conclusions:

• Glutathione reductase catalyzes the reduction of GSSeSG to H2Se through a stepwise process.
• The proposed pathway involves the formation of GSSeH as an intermediate.
• This enzymatic pathway is significant for selenium detoxification and metabolism.