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Reprinted from BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Volume 52, Number 3, June 8, 1973
 

Summary: Reprinted from BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Volume 52, Number 3, June 8, 1973
@ 1973 by Academic Press, Inc. Printed in U.S.A.
Vol. 52, No. 3,1973 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
SUEEROXIDE BEDUCTION AS A MECHANISM O? ASCORBATE-
STIlqTJIATED OAYGEN UPTAKE BY ISOLAJPEB CHLOROPLASTS
J.?. Alien and. B.O. Hall
University of London, King's College, Botany Department,
68 Half Moon Lane, London SE24 9JF
Received A p r i l 1 6 , 1 9 7 3
SiiT3i&iT?Y: Addition of l@ascorbate t o isolated chloroplasts with methyl
viologen (W) a s electron acceptor trebled the r a t e of oxygen uptake and
decreased, the ADP/O r a t i o t o a t h i r d of t h a t with no ascorbate present.
These effects of ascorbate were reversed by superoxide dismutase (SOD),
which in the absence of ascorbate had l i t t l e e f f e c t on Or. uptake o r AEP/O
r a t i o . A chloroplast-associated SOD a c t i v i t y equivalent t o 500 units/mg
chlorophyll was detected,, The e f f e c t s of ascorbate and SOD on Og uptake
were similar i n both coupled and uncoupled chloroplasts. The r e s u l t s a r e
consistent with the hypothesis t h a t ascorbate stimulates 0, uptake by
reduction of superoxide, which i s formed by autoxidation of the added

  

Source: Allen, John F. - School of Biological and Chemical Sciences, Queen Mary, University of London

 

Collections: Renewable Energy; Biology and Medicine