Salema M, Lolkema J S, San Romão M V, Lourero Dias M C
Instituto de Tecnologia Química e Biológica, Universdade Nova de Lisboa, Portugal.
J Bacteriol. 1996 Jun;178(11):3127-32. doi: 10.1128/jb.178.11.3127-3132.1996.
In cells of Leuconostoc oenos, the fermentation of L-malic acid generates both a transmembrane pH gradient, inside alkaline, and an electrical potential gradient, inside negative. In resting cells, the proton motive force ranged from -170 mV to -88 mV between pH 3.1 and 5.6 in the presence Of L-malate. Membrane potentials were calculated by using a model for probe binding that accounted for the different binding constants at the different pH values at the two faces of the membrane. The delta psi generated by the transport of monovalent malate, H-malate-, controlled the rate of fermentation. The fermentation rate significantly increased under conditions of decreased delta psi, i.e., upon addition of the ionophore valinomycin in the presence of KCl, whereas in a buffer depleted of potassium, the addition of valinomycin resulted in a hyperpolarization of the cell membrane and a reduction of the rate of fermentation. At the steady state, the chemical gradient for H-malate- was of the same magnitude as delta psi. Synthesis of ATP was observed in cells performing malolactic fermentation.
在酒酒球菌细胞中，L-苹果酸的发酵产生了一个跨膜pH梯度（内部呈碱性）和一个电势梯度（内部呈负电）。在静息细胞中，在存在L-苹果酸的情况下，质子动力势在pH 3.1至5.6之间的范围为-170 mV至-88 mV。膜电位是通过使用一个探针结合模型计算得出的，该模型考虑了膜两侧在不同pH值下的不同结合常数。单价苹果酸（H-苹果酸根离子）运输产生的Δψ控制着发酵速率。在Δψ降低的条件下，即当在存在KCl的情况下添加离子载体缬氨霉素时，发酵速率显著增加，而在低钾缓冲液中，添加缬氨霉素会导致细胞膜超极化并降低发酵速率。在稳态时，H-苹果酸根离子的化学梯度与Δψ大小相同。在进行苹果酸-乳酸发酵的细胞中观察到了ATP的合成。
