title: Steady-state kinetics of the photosystem I reaction in chloroplasts of Dunaliella which contain variable concentrations of plastocyanin.
abstract: 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.
authors.affiliation: Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, D-7750, Konstanz, Germany (FRG).
authors.forename: G
authors.initials: G
authors.lastname: Sandmann