The involvement of H sub 2 O sub 2 in photoinhibition of photosystem II
- Arizona State Univ., Tempe (United States)
The involvement of H{sub 2}O{sub 2} in the inactivation of photosystem II and degradation of the D1 protein induced by high light intensities was investigated. Depletion of C1{sup {minus}} from the oxygen-evolving complex (OEC), which accelerates the rate of photoinhibition, allows the OEC to oxidize water to H{sub 2}O{sub 2} rather than to O{sub 2}. The rate of photoinhibition in thylakoids was accelerated more than 2 fold when the endogenous F-catalase is inhibited by 1 mM KCN. The acceleration of photoinhibition by KCN was observed for both C1{sup {minus}}-depleted and C1{sup {minus}}-sufficient thylakoids, which suggests a second site for the formation of H{sub 2}O{sub 2} in PSII. The ability of the reducing side of PSII to reduce O{sub 2} to H{sub 2}O{sub 2} during photoinhibition was eliminated by the addition of the coupled enzyme systems: glucose oxidase with glucose and horseradish peroxidase with catechol. The slow rate of photoinhibition in the presence of these coupled enzyme systems suggests that a second site of photoinhibitory H{sub 2}O{sub 2} production is from O{sub 2} on the reducing side of PSII. Addition of H{sub 2}O{sub 2} was found to induce a low temperature EPR signal centered at g = 2 which is similar to the EPR signal attributed to the induction of photoinhibition in C1{sup {minus}}-depleted samples. A comparison of the degradation products of the D1 protein induced by a 60 min exposure to either photoinhibitory illumination or to exogenous H{sub 2}O{sub 2} was also made using a polyclonal antibody to D1. From these results the authors propose that photoinhibition and D1 degradation is induced by H{sub 2}O{sub 2} produced by PSII at high light intensities. H{sub 2}O{sub 2} may inactivated D1 by crosslinking two tyrosines on the protein and/or by cleavage of the D1 at the three positions where glycine follows asparagine in the sequence.
- OSTI ID:
- 5400219
- 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
HYDROGEN PEROXIDE
TOXICITY
PHOTOSYNTHETIC REACTION CENTERS
PHOTOCHEMISTRY
CATALASE
CYANIDES
INACTIVATION
INHIBITION
THYLAKOID MEMBRANE PROTEINS
CHEMISTRY
ENZYMES
HYDROGEN COMPOUNDS
MEMBRANE PROTEINS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PEROXIDASES
PEROXIDES
PROTEINS
560300* - Chemicals Metabolism & Toxicology