Glutathione reductase Sigma Aldrich GpoA Glutathione Peroxidase Links Oxidative Stress Response, Antibiotic Persistence, and Virulence in Streptococcus pneumoniae bioRxiv Glutathione reductase G3664 100UN SIGMA ALDRICH SLS Frontiers Assigning function to active site residues of Schistosoma mansoni thioredoxin glutathione reductase from analysis of transient state reductive half reactions with variant forms of the enzyme