Brigitte Depka

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alpha-Tocopherol concentrations were determined at low and high light intensities and compared with the rate of photosynthesis, photosystem II (PS II) and its reaction center D1 protein. Blocking of tocopherol biosynthesis at the 4-hydroxyphenylpyruvate dioxygenase by the herbicide pyrazolynate led to a quick disappearance of alpha-tocopherol in high light,(More)
The carotenoid composition was investigated during enhanced D1 protein turnover in Chlamydomonas reinhardtii exposed to high light. After 2 h of high light there was no loss of the D1 protein yet. However, the beta-carotene content was significantly reduced. In parallel, an increase of the zeaxanthin content was found, which was higher than can be accounted(More)
Rapid degradation of the photosystem-II reaction center protein, D1, is driven by visible and ultraviolet irradiance at low photon-flux in the intact plant. We find that all inhibitors of electron flow that replace bound plastoquinone (QB) from its niche on D1 inhibit UV-B-driven D1 degradation, but only some inhibit visible light-driven degradation.(More)
The sensitivity of the D-1 and D-2 polypeptide subunits of photosystem II towards trypsin treatment of the thylakoid membrane has been probed with specific antibodies. As long known, electron flow from water to ferricyanide becomes inhibitor insensitive after this trypsin treatment. We show that under these conditions the D-2 polypeptide is cut by trypsin(More)
Inhibitors of the phytoene desaturase in carotene biosynthesis were tested in the enhanced rapid turnover of the D1 protein of photosystem II in high light exposure of Chlamydomonas reinhardtii cells. After 1 h high light on heterotrophically grown cells in the presence of norflurazon or fluridone, photosynthesis activity in vivo and PS II activity in vitro(More)
Isoxaflutole or pyrazolate inhibition of tocopherol and plastoquinone biosynthesis in the green alga Chlamydomonas reinhardtii Dang leads to the inactivation of photosystem II and the degradation of its reaction centre D1 protein when exposed to strong light. Cell-permeable short-chain derivatives of plastoquinone and tocopherol were tested in the reversal.(More)
Very briefly, the present state of knowledge on the latent, lumen oriented polyphenol oxidase (PPO) of the chloroplast is reviewed. The location of PPO in the thylakoid membrane was described by D. Arnon 46 years ago. The N-terminus sequence of the spinach enzyme is reported. A historical sketch is given of the discovery of photophosphorylation and Arnon's(More)
The first three enzymatic steps of assimilatory sulfate reduction in chloroplasts of higher plants have been investigated with emphasis on the influence of adenosine-mono-and-diphosphate upon the formation of APS, PAPS and bound sulfite. The data show that the activation process is governed by the energy charge of the chloroplast. The regulatory step is(More)
The new bleaching herbicidal compound N,N-diethyl-N-(2-undecynyl)amine (NDUA) is identified here as an inhibitor of lycopene cyclase and is compared with the known cyclase inhibitors N,N-diethyl-N-[2-(4-chlorophenylthio)ethyl]amine (CPTA) and N,N-diethyl-N-[2-(4-methylphenoxy)ethyl]amine (MTPA). HPLC separation of chloroplast pigments shows lycopene(More)
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