Participation of adenylate kinase in the regulation of chloroplast energy exchange

Kartashov, I. M.

doi:10.1134/s0006350909050078

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“…In mitochondria, the transfer of electrons can be provided by enzymes such as adenylate kinase and creatinine kinase [24,25]. In chloroplasts, this process occurs due to adenylate kinase according to our data [26]. In conclusion, it is important to note that the regulation of diffusion of adenine nucleotides by enzymes with variable activities is biologically more favorable because this makes it possible to avoid the inertia of the energy exchange and allows the fitting of the transport of energy to the various factors in accor dance with the needs of the cell.…”

Section: Discussionmentioning

confidence: 59%

The effect of viscosity-increasing agents on ATP synthesis in chloroplast thylakoids

2015

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The effect of an increase in the viscosity of the medium on cyclic photophosphorylation in chlo roplast thylakoids and the Ca 2+ dependent ATP hydrolysis by the chloroplast coupling factor CF 1 was stud ied. Using 0.1-0.2 mM ADP, it was found that the rate of ATP synthesis decreases after the addition of various agents that increase the viscosity of the medium (sucrose, dextran 40, or polyethylene glycol 6000) provided that these agents cause neither uncoupling nor electron transport inhibition in the absence of ADP. Dextran and polyethylene glycol inhibited ATP synthesis by 50% when their concentrations were much lower (6-10%) than that of sucrose (30-40%), while 50% inhibition of the Ca 2+ dependent ATP hydrolysis by CF 1 ATPase was observed at higher concentrations of dextran and polyethylene glycol (9-13%) and lower con centrations of sucrose (about 20%). For ADP, the effective Michaelis constant (K M ) was shown to increase by factors of 2-3 with increasing viscosity, while the maximum rate of cyclic photophosphorylation remained virtually unchanged. The dependence of K M on the medium viscosity can serve as a criterion for the operation of diffusion controlled photophosphorylation. Possible mechanisms of the diffusion of ADP and ATP are discussed.

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Section: Discussionmentioning

confidence: 59%