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Summary: Vol. 66, No. 1, 1975 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
A TWO-STEP MECHANISM FOR THE PHOTOSYMTHETIC REDUCTIOH
OF OXYGEN BY PERREDOXM
J.F. Alien
University of London, King's College, Department of Plant
Sciences, 68 Half Moon Lane, London SE24 9JP U.K.
Address from October 1st 1975; Botany School, South parks
Road, Oxford OX1 3RA U.K.
Received June 2,1975
SUMABY It is proposed that autoxidation of plant-type
ferredoxin involves the reduction of oxygen to superoxide
and of superoxide to peroxide. This mechanism aceounts for
an inhibition by superoxide dismutase of ferredoxin-mediated,
photosynthetic oxygen uptake by isolated chloroplasts, and
for an insensitivity of this reaction to ascorbate. Preliminary
evidence for an inhibition by superoxide dismutase of
autoxidation of chemically-reduced ferredoxin is presented,
and some implications of the two-step mechanism are discusssd.
Photosynthetic oxygen uptake is a result of autoxidation
of a low-potential electron acceptor. Where an artificial
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