Wainio W W
Int Rev Cytol. 1985;96:29-50. doi: 10.1016/s0074-7696(08)60593-8.
It is argued that a proton concentration difference and/or a membrane potential is not the form into which the free energy of the oxidation-reduction reactions of the mitochondrial respiratory chain is first transduced. It is suggested that the search for a chemical intermediate should be continued in spite of the conclusion by some investigators that the chemical hypothesis is untenable. It is asked whether pH changes when measured in solutions containing mitochondria can be interpreted as evidence for H+ movements, also, whether there is a continuous, renewable and stable electrochemical proton concentration difference (delta mu H+) across the mitochondrial membrane, and whether in fact the delta mu H+ is a necessary intermediate in the synthesis of ATP. The four postulates of Mitchell's chemiosmotic hypothesis of energy transduction are discussed point by point. It is agreed that "The systems are plugged through a topologically closed insulating membrane," which probably is not "a nonaqueous osmotic barrier," and which probably does not have an unusually "low permeability to solutes and to H+ and OH- in particular" when compared with other membranes. There is disagreement with the statement that "Respiratory and photoredox systems are chemiosmotic membrane-located protonmotive chains" in that it is suggested by others that chemiosmosis is chemically nonexistent and that thermodynamically it would lack control. The subsequent statement, "having a characteristic----H+/2 epsilon- stoichiometry," is rendered uncertain by the experimental findings of values greater than 2H+/2 epsilon-/site and probably as large as 4H+/2 epsilon-/site. The proposal that "The synthetase is a chemiosmotic membrane-located reversible motive ATPase" requires the assumption that the ATP synthetase is the same enzyme as the ATPase, but functioning in the reverse direction. It is considered possible that there are two enzymes in the multi-subunit ATPase complex: one the hydrolase, and the other the synthetase. The further proposal, "having characteristic----H+/P stoichiometry" requires that the ratio be 2 according to Mitchell. However, values of 3, as well as larger values, have been reported by others, which introduces a large element of uncertainty. There is no disagreement with the statement that "There are proton-linked (or hydroxyl ion-linked) solute porter systems for osmotic stabilization and metabolite transport." In fact, this may be the principal reason for having proton efflux or "proton-pumping.''(ABSTRACT TRUNCATED AT 400 WORDS)
有人认为，质子浓度差和/或膜电位并非线粒体呼吸链氧化还原反应自由能最初转化的形式。尽管一些研究者得出化学假说站不住脚的结论，但仍建议继续寻找化学中间体。文中提出了几个问题：在含有线粒体的溶液中测量时，pH变化能否被解释为H⁺移动的证据；线粒体膜上是否存在连续、可再生且稳定的电化学质子浓度差（δμH⁺）；实际上，δμH⁺是否是ATP合成中必要的中间体。米切尔化学渗透能量转化假说的四个假设被逐一讨论。大家一致认同“系统通过拓扑封闭的绝缘膜连接”，这可能不是“非水渗透屏障”，与其他膜相比，它对溶质尤其是H⁺和OH⁻的渗透性可能并非异常低。对于“呼吸和光氧化还原系统是位于化学渗透膜上的质子动力链”这一说法存在分歧，因为其他人认为化学渗透在化学上并不存在，且在热力学上缺乏控制。随后的说法“具有特征性的——H⁺/2ε化学计量比”因实验发现的值大于2H⁺/2ε/位点且可能高达4H⁺/2ε/位点而变得不确定。“合成酶是位于化学渗透膜上的可逆动力ATP酶”这一提议需要假设ATP合成酶与ATP酶是同一种酶，但作用方向相反。有人认为在多亚基ATP酶复合物中可能存在两种酶：一种是水解酶，另一种是合成酶。进一步的提议“具有特征性的——H⁺/P化学计量比”要求根据米切尔的说法该比例为2。然而，其他人报告的值为3以及更大的值，这带来了很大的不确定性。对于“存在用于渗透稳定和代谢物运输的质子连接（或羟基离子连接）溶质转运系统”这一说法没有分歧。事实上，这可能是质子外流或“质子泵浦”的主要原因。
