Figure 1. Simplified scheme for intracellular redox systems.
NADH produced during glycolysis and the tricarboxylic acid (TCA) cycle is consumed by the electron transfer chain. NADPH generated by the catalysis of glucose-6-phosphate dehydrogenase (G6PD) is utilized to reduce oxidized glutathione (GSSG) by glutathione reductase (GR) or oxidized thioredoxin (Trx) by thioredoxin reductase (TR).