REDOX REGULATION: A Broadening Horizon

Initially discovered in the context of photosynthesis, regulation by change in the redox state of thiol groups (S−S ↔ 2SH) is now known to occur throughout biology. Several systems, each linking a hydrogen donor to an intermediary disulfide protein, act to effect changes that alter the activity of target proteins: the ferredoxin/ thioredoxin a small protein, reduced enzymatically by NADPH or ferredoxin, that is active in thiol/disulfide exchange and results in regulation or substrate conversion system, comprised of reduced ferredoxin, a thioredoxin, and the enzyme, ferredoxin-thioredoxin reductase; the NADP/thioredoxin system, including NADPH, a thioredoxin, and NADP-thioredoxin reductase; and the glutathione/…