Characterization of superoxide production by isolated pea thylakoids
- Duke Univ., Durham, NC (United States)
During photosynthesis chloroplasts univalently reduce molecular oxygen to superoxide through autoxidations in the electron transport chain. Cytochrome c reduction was used to assay superoxide production in illuminate pea thylakoids under a variety of conditions. Superoxide dismutase was found to inhibit the reaction by 80%, indicating that cytochrome c reduction is primarily mediated by superoxide. This was further supported by the observation that the highest rates of cytochrome c reduction occurred in the presence of methyl viologen, an autoxidizable redox carrier that accepts electrons from photosystem I. The reaction was fully suppressed by DCMU, demonstrating a requirement for electron transport. In the presence of the plastoquinone antagonist DBMIB the rate of cytochrome c reduction increased substantially. This indicates that under conditions where electron transport to photosystem I is blocked, autoxidation reactions can occur on the reducing side of photosystem II to maintain Q{sub A} in the oxidized state. Superoxide production at sites other than the reducing side of photosystem I may thus represent an important pathway for dissipating excess excitation energy.
- OSTI ID:
- 5514162
- Report Number(s):
- CONF-9107184-; CODEN: PPYSA
- Journal Information:
- Plant Physiology, Supplement; (United States), Vol. 96:1; Conference: Annual meeting of the American Society of Plant Physiology, Albuquerque, NM (United States), 28 Jul - 1 Aug 1991; ISSN 0079-2241
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
PHOTOSYNTHETIC REACTION CENTERS
PHYSIOLOGY
BIOLOGICAL PATHWAYS
CHARGE EXCHANGE
CYTOCHROME OXIDASE
PISUM
SUPEROXIDE DISMUTASE
SUPEROXIDE RADICALS
ENZYMES
HAEM DEHYDROGENASES
LEGUMINOSAE
MAGNOLIOPHYTA
MAGNOLIOPSIDA
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PLANTS
PROTEINS
RADICALS
551000* - Physiological Systems