Steady-state kinetics of the photosystem I reaction in chloroplasts of Dunaliella which contain variable concentrations of plastocyanin

Photosynthesis Research
G Sandmann


The endogenous plastocyanin (PC) concentrations of Dunaliella cultures were varied from 0.3 to 3.1 molecules per pigment 700 (P700) by decreasing the Cu(+) supply of the nutrient. With these cultures the amount of PC which is sufficient for maximum photosynthesis in intact cells was determined to be about 1 to 1.5 PC/P700. Chloroplasts were also prepared from these cells and were employed in enzyme kinetic measurements of the PSI reaction from ascorbate reduced diaminodurene (DAD) to methylviologen/O2. The k m value for DAD in this reaction was 106 μM. A decrease of the endogenous PC concentration caused no change of the k m value but affected the V max in the DAD-dependent reaction. A similar interference of the PC concentration on the maximum reaction rate could also be observed when the light intensity was varied.


May 9, 1967·Biochimica Et Biophysica Acta·J J Lightbody, D W Krogmann
Oct 1, 1973·Archives of Biochemistry and Biophysics·J N SiedowA San Pietro
Dec 3, 1980·Biochimica Et Biophysica Acta·W HaehnelH Krause

Related Concepts

Plastocyanin Activity
Ascorbate Measurement
Photosystem I

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