The
relation of the light-dependent and light-triggered adenosine
triphosphatases to photophosphorylation
Bennun, A. and Avron, M.
1. Wide specificity for nucleoside triphosphates was found
for light-dependent and light-triggered ATPase (ATP phosphohydrolase,
EC 3.6.1.3) of isolated chloro¬plasts.
2. The reported wide specificity of photophosphorylation for
nucleoside di-phosphates has been confirmed under more rigorous
conditions. Similar wide specificity was found for the same
compounds as inhibitors of the light-requiring ATPases.
3. The affinity of photophosphorylation for ADP and GDP was
found to be similar under conditions optimal for photophosphorylation,
but very different under conditions optimal for the light-requiring
ATPases.
4. The affinity of the light-requiring ATPases for ADP and
GDP as competitive inhibitors was found to be identical to
the affinity of photophosphorylation for the compounds under
the same experimental conditions.
5. Several inhibitors acted similarly on the light-requiring
ATPases and on photophosphorylation.
6. A coupling factor, previously reported to be essential
for photophosphory¬lation, was found to be essential also
for the light-requiring ATPases.
7. It is suggested that the evidence presented strongly supports
the hypothesis that the light-requiring ATPases of chloroplasts
share part of the energy-transport path used for ATP production
during photophosphorylation.
Biochimica et Biophysica Acta, 109, (1965), 117-127