Uni‐site catalysis in thylakoids

FEBS Letters

Fromme, Petra¹  Gräber, Peter² 

[1] Max Volmer Institut für Biophysikalische und Physikalische Chemie, Technische Universität Berlin, Str.d. 17. Juni 135 D-1000 Berlin 12, FRG;Biologisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 7000 Stuttgart 80, FRG

关键词: Chloroplast;    H+-ATPase;    CFoF1;    ATP synthesis;    ATP-Pi exchange;    Uni-site catalysis;    CFoF1;    H+-translocating ATPase (‘ATP-synthase’) from chloroplasts;    Chl;    chlorophyll;   

DOI  :  10.1016/0014-5793(90)81165-K

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

ATP-hydrolysis was measured with thylakoid membranes during continuous illumination. The concentrations of free and enzyme-bound ATP, ADP and P_i were measured using either cold ATP, [γ-³²P]ATP or [¹⁴C]ATP. The concentration of free ATP was constant, free ADP and enzyme-bound ATP were below the detection limit. Nevertheless, [γ-³²P]ATP was bound, hydrolyzed and ³²P_i was released. The ADP was not released from the enzyme but cold Pi was bound from the medium, cold ATP was resynthesized and released. A quantitative analysis gave the following rate constants: ATP-binding k_ATP = 2·10⁵ M⁻¹s⁻¹, ADP-release: k_ADP <10⁻²s⁻¹, P_i-release: k_Pi = 0.1 s⁻¹. These rate constants are considerably smaller than under deenergized conditions. The rate constant for the release of ATP can be estimated to be at least 0.2 s⁻¹ under energized conditions. Obviously, energization of the membrane, i.e. protonation of the enzyme leads mainly to a decrease of the rate of ATP-binding, to an increase of the rate of ATP release and to a decrease of the rate of ADP-release.

【 授权许可】

Unknown