Hess B
Ciba Found Symp. 1975(31):369-92. doi: 10.1002/9780470720134.ch20.
When, on addition of a suitable substrate, a chemical potential is applied to an enzymic process such as glycolysis or respiration, whether in solution or membrane-bound, all components of the process pass into a nonequilibrium state, which might be steady or non-steady and which produces the following phenomena: (1) The reactants of each enzymic reaction are displaced from their equilibrium concentration, and energy is dissipated; (2) Part of each enzyme is transferred to a transition state of its catalytic function as well as isosteric and allosteric controlling functions, displaying local and gross conformation changes, and a rate-controlling state is generated; (3) In cyclic portions of a process futile events and chemical interconversion may occur; (4) In self- and cross-coupled portions of a process, oscillation with periodic changes of states and spatial propagation as well as instabilities may be observed; (5) At each step of a process, depending on the rate of flux and the specific enzymic function, a varying proportion of the free energy changes--which are concentration-dependent and derived from the overall potential of the system-is contributed to the control of flux rates. This will be exemplified for enzymes of bioenergetic pathways.
当向诸如糖酵解或呼吸作用这样的酶促过程添加合适的底物并施加化学势时，无论该过程是在溶液中还是与膜结合，过程的所有组分都会进入非平衡状态，这种状态可能是稳定的或非稳定的，并产生以下现象：（1）每个酶促反应的反应物偏离其平衡浓度，能量被耗散；（2）每个酶的一部分转变为其催化功能以及别构和变构控制功能的过渡态，呈现局部和整体构象变化，并产生速率控制状态；（3）在过程的循环部分可能发生无效事件和化学相互转化；（4）在过程的自耦合和交叉耦合部分，可能观察到状态的周期性变化、空间传播以及不稳定性的振荡；（5）在过程的每一步，根据通量速率和特定的酶功能，自由能变化的不同比例（其取决于浓度并源自系统的总电势）有助于控制通量速率。这将以生物能途径的酶为例进行说明。
