Palmer T, Jackson J B
School of Biochemistry, University of Birmingham, UK.
Biochim Biophys Acta. 1992 Feb 21;1099(2):157-62.
Chromatophores from Rhodobacter capsulatus were incubated in the dark with NADPH and acetylpyridineadenine dinucleotide (AcPdAD+) in the presence of different concentrations of myxothiazol. The transhydrogenase activity was monitored until an appropriate mass action ratio, [AcPdAD+][NADPH]/[AcPdADH][NADP+], was reached. The sample was then illuminated and the initial rate of either AcPdAD+ reduction by NADPH or AcPdADH oxidation by NADP+ was recorded. The ratio of H+ translocated per H- equivalent transferred by transhydrogenase was calculated from the value of the membrane potential (delta pH = 0) at which illumination caused no net reaction in either direction. The mean value for the H+/H- ratio was 0.55. At greater values of [AcPdAD+][NADPH]/[AcPdADH][NADP+] than were employed in the above experiments and over a wider range of concentrations of myxothiazol, it was found that incremental increases in the membrane potential always gave rise to a decrease, never an increase in the rate of AcPdAD+ reduction. In contrast to the H(+)-ATP synthase, there is no evidence of any activation/deactivation of H(+)-transhydrogenase by the protonmotive force.
将来自荚膜红细菌的载色体在黑暗中与NADPH和乙酰吡啶腺嘌呤二核苷酸（AcPdAD+）一起，在不同浓度的粘噻唑存在下孵育。监测转氢酶活性，直到达到合适的质量作用比[AcPdAD+][NADPH]/[AcPdADH][NADP+]。然后将样品光照，并记录NADPH还原AcPdAD+或NADP+氧化AcPdADH的初始速率。转氢酶每转移一个H-等价物所转运的H+比例，是根据光照在任一方向都不引起净反应时的膜电位值（δpH = 0）计算得出的。H+/H-比例的平均值为0.55。在比上述实验中使用的[AcPdAD+][NADPH]/[AcPdADH][NADP+]值更高，且粘噻唑浓度范围更宽的情况下，发现膜电位的增量增加总是导致AcPdAD+还原速率降低，而不是增加。与H(+)-ATP合酶相反，没有证据表明质子动力对H(+)-转氢酶有任何激活/失活作用。
