Glutathione reductase catalytic cycle MedLink Neurology Glutathione NADPH + H+ NADP+ FAD Pentose Phosphate Pathway Riboflavin Glutamate (Oxidized glutathione) (Reduced glutathione, a s Glutathione Reductase human Item Scheme showing the enzymatic reactions that catalyze the pyruvate dehydrogenase complex, including pyruvate dehydrogenase activity and diaphorase activity of DLD (A) as well as the glutathione reductase peroxidase activity (B).