The Contribution of Light-Dependent Bicarbonate Uptake in Thylakoid Membrane Energization
Illumination of the well stirred suspension of isolated spinach chloroplasts induced CO2 uptake (up to 320 nmol CO2/mg chlorophyll) from air phase over suspension. The process started immediately after onset of illumination, developed during 15-20 sec and completely reversed for the same time after switching off the light. Uncouplers (gramicidine D, NH4Cl) inhibited the light-induced CO2 uptake. The value of light-induced CO2 uptake was dependent on carbonic anhydrase (CA) activity and inhibited by CA inhibitors - lipophylic ethoxyzolamide (EZ) and water-soluble acetazolamide. The effect of exogenic bicarbonate and inhibitors of carbonic anhydrase on the rate of photophosphorylation was examined in the pH range 7.0-8.2. It was shown that exogenic bicarbonate (3-6 mmol) effectively stimulated photophosphorylation. The bicarbonate-induced enhancement of photophosphorylation showed a marked pH dependence, with the greatest response occurring at pH near 7.0. Both EZ and AZ reduced the stimulating effect of HCO3- on the rate of photophosphorylation. It is concluded that lightinduced ATP synthesis depends not only on exogenic bicarbonate, but also on the activity of carbonic anhydrase that rapidly converts the forms of carbonic acid thereby facilitating protons removal from sites of their evolution.
Proton transfer Bicarbonate Photophosphorylation Carbonic anhydrase Thylakoid membrane
Zolotareva EK Polishchuk OV Semenikhin AV Onoiko EB
M.G. Kholodny Institute of botany of the National Academy of Sciences of Ukraine Tereschenkivska str., 2,01601, Kyiv-1, Ukraine
国际会议
15th International Conference on Photosynthesis(第15届国际光合作用大会)
北京
英文
197-201
2010-08-22（万方平台首次上网日期，不代表论文的发表时间）