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ANTIOXIDANTS & REDOX SIGNALING Volume 5, Number 1, 2003
 

Summary: ANTIOXIDANTS & REDOX SIGNALING
Volume 5, Number 1, 2003
Ma ry Ann Liebert, In c.
Forum Original Research Communication
Superoxide as an Obligatory, Catalytic Intermediate
in Photosynthetic Reduction of Oxygen
by Adrenaline and Dopamine
JOHN F.ALLEN
ABSTRACT
The superoxide anion radical is known to be the first product of photosynthetic reduction of oxygen mediated
by a variety of electron carriers. The effectiveness of many of these electron carriers as herbicides, and the
toxicity of the superoxide they produce, have been suggested to rule out oxygen reduction as a physiological
component of normal photosynthesis. Here results with isolated spinach chloroplasts are presented that dem-
onstrate that the related catecholamines adrenaline and dopamine mediate photosynthetic reduction of
oxygen. Complete inhibition by added superoxide dismutase of light-dependent oxygen uptake by isolated
chloroplasts and of the electron transport it supports indicates that superoxide is an obligatory catalytic inter-
mediate, not a product, in adrenaline- and dopamine-mediated oxygen reduction. These compounds might
function as chemical analogues of a proposed natural mediator, or oxygen-reducing factor, that allows oxygen
reduction to participate in energy transduction in photosynthesis. The identity of the putative natural media-
tor and the role of oxygen reduction in photosynthesis are discussed. The fully oxidized form of adrenaline,

  

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

 

Collections: Renewable Energy; Biology and Medicine