Abstract
Thiol-treated S. oleracea chloroplast fructose bisphosphatase (EC 3.1.3.11) is severely inhibited by H2O2, while the freshly purified enzyme is little affected. Dithiothreitol reverses inhibition by H2O2, indicating that essential thiol groups are oxidized during H2O2 inactivation. A new role for the dithiol and thioredoxin systems that are operative in illuminated chloroplasts is proposed.