Reduction of S-Sulfoglutathione by Cyanobacterial Ferredoxin-sulfite Reductase

Abstract

S-Sulfoglutathione is reduced by reduced ferredoxin and ferredoxin dependent sulfite reductase (Fd-SiR) from the cyanobacterium Spimlina platensis. The Km value calculated from a Lineweaver-Burk plot of the data was 6.0 × 10^-5M. A plot of ferredoxin concentration versus reduction activity of S-sulfoglutathione (GSSO₃H) of Fd-SiR yielded a sigmoidal curve, giving a Hill coefficient (n) of 3.0. Antiserum against Fd-SiR strongly inhibits this reaction. In an experiment using a crude cell extract, the GSSO₃H reducing activity was only found at the site of Fd-SiR in gel filtration and immunoblotting.