Department of Microbiology, University of Groningen, 9751 NN Haren, The Netherlands.
Appl Environ Microbiol. 1986 Jan;51(1):95-100. doi: 10.1128/aem.51.1.95-100.1986.
The hydrolysis of the dipeptide leucyl-leucine by whole cells of Streptococcus cremoris Wg(2) was dependent on the presence of the energy source lactose. Incubation of cells with uncouplers or ATPase inhibitors prevented the increase of peptidase activity upon the addition of lactose. Incubation with the ionophore nigericin resulted in decreased peptide hydrolysis activity, while incubation with valinomycin led to increased hydrolysis activity. In the presence of nigericin the DeltapH component of the proton motive force was decreased, while the electrical potential was increased. With valinomycin, the electrical potential was collapsed and the DeltapH was increased. When the external pH was decreased from 8 to 5, the rate of peptide hydrolyzing activity by whole cells increased with increasing DeltapH component. In contrast, the peptide hydrolyzing activity in the cell extract decreased with decreasing external pH. These results indicate that the DeltapH component of the proton motive force determines the leucyl-leucine hydrolyzing activity in S. cremoris Wg(2).
乳酪链球菌(Streptococcus cremoris Wg(2))的完整细胞将二肽亮氨酰-亮氨酸水解,这依赖于能源乳糖的存在。用解偶联剂或 ATP 酶抑制剂孵育细胞可防止在加入乳糖时肽酶活性的增加。用离子载体 Nigericin 孵育会导致肽水解活性降低,而用缬氨霉素孵育则会导致水解活性增加。在 Nigericin 的存在下,质子动力势的ΔpH 分量降低,而电势能增加。用缬氨霉素时,电势能崩溃,ΔpH 增加。当外部 pH 值从 8 降低到 5 时,整个细胞的肽水解活性随ΔpH 分量的增加而增加。相比之下,细胞提取物中的肽水解活性随外部 pH 值的降低而降低。这些结果表明,质子动力势的ΔpH 分量决定了乳酪链球菌(S. cremoris Wg(2))中亮氨酰-亮氨酸的水解活性。