Thayer J R, Huffaker R C
J Bacteriol. 1982 Jan;149(1):198-202. doi: 10.1128/jb.149.1.198-202.1982.
A kinetic evaluation of initial rates of nitrate transport at concentrations between 1 microM and 1 mM indicated the presence of two transport processes. Analysis of the contribution of each process to the total activity permitted the determination of kinetic constants (Km) of 4.9 microM and 4.2 mM for the high-and low-affinity systems, respectively. The ratio of the maximal velocity of the high-affinity system to that of an apparent low-affinity system was about 0.3. Both systems were inhibited by the presence of NH4+ in the transport assay. Growth in the presence of equimolar NO3- and NH4+ repressed the synthesis of both systems when compared with growth in NO3- alone.
对浓度在1微摩尔至1毫摩尔之间的硝酸盐转运初始速率进行的动力学评估表明存在两种转运过程。分析每个过程对总活性的贡献,得出高亲和力系统和低亲和力系统的动力学常数(Km)分别为4.9微摩尔和4.2毫摩尔。高亲和力系统的最大速度与表观低亲和力系统的最大速度之比约为0.3。在转运试验中,两种系统均受到NH4+存在的抑制。与仅在NO3-中生长相比,在等摩尔NO3-和NH4+存在下生长会抑制两种系统的合成。