CYTOPLASMIC STEPS OF PEPTIDOGLYCAN SYNTHESIS IN ESCHERICHIA-COLI
CYTOPLASMIC STEPS OF PEPTIDOGLYCAN SYNTHESIS IN ESCHERICHIA-COLI
复制标题
DOI：
10.1128/jb.151.3.1109-1117.1982
复制
发表时间：
1982-01-01
影响因子：
3.2
通讯作者：
VANHEIJENOORT, J
中科院分区：
文献类型：
--
作者：
MENGINLECREULX, D;FLOURET, B;VANHEIJENOORT, J
大多数肽聚糖合成的细胞质前体的细胞池水平测定正常生长的大肠杆菌K-12细胞。特别是，一个方便的方法分析尿苷核苷酸前体含量的凝胶过滤和反相高压液相色谱技术相结合的发展。测定了四种合成酶催化L-丙氨酸、D-谷氨酸、meso-二氨基庚二酸和D-丙氨酰-D-丙氨酸与尿苷二磷酸-N-乙酰胞壁酸的逐步加成反应的酶促参数。值得注意的是，L-丙氨酸、D-谷氨酸、内消旋-二氨基庚二酸和D-丙氨酰-D-丙氨酸的合并水平远高于这些底物测定的Km值，而尿苷核苷酸前体的摩尔浓度低于相应Km值或与相应Km值的数量级大致相同。考虑到所获得的数据，尝试将D-谷氨酸、内消旋-二氨基庚二酸和D-丙氨酰-D-丙氨酸添加酶的体外活性与它们的体内功能进行比较，所述体内功能由合成的肽聚糖的量表示。结果还表明，在正常生长条件下，这些添加活性在细胞中并不过量，但它们的量似乎根据肽聚糖合成的要求进行了调整。在所考虑的不同体外条件下，仅观察到低水平的L-丙氨酸添加活性。
The cellular pool levels of most of the cytoplasmic precursors of peptidoglycan synthesis were determined for normally growing cells of Escherichia coli K-12. In particular, a convenient method for analyzing the uridine nucleotide precursor contents was developed by associating gel filtration and reverse-phase high-pressure liquid chromatography techniques. The enzymatic parameters of the four synthetases which catalyze the stepwise addition of L-alanine, D-glutamic acid, meso-diaminopimelic acid, and D-alanyl-D-alanine to uridine diphosphate-N-acetylmuramic acid were determined. It was noteworthy that the pool levels of L-alanine, D-glutamic acid, meso-diaminopimelic acid, and D-alanyl-D-alanine were much higher than the Km values determined for these substrates, whereas the molar concentrations of the uridine nucleotide precursors were lower than or about the same order of magnitude as the corresponding Km values. Taking into consideration the data obtained, an attempt was made to compare the in vitro activities of the D-glutamic acid, meso-diaminopimelic acid, and D-alanyl-D-alanine adding enzymes with their in vivo functioning, expressed by the amounts of peptidoglycan synthesized. The results also suggested that these adding activities were not in excess in the cell under normal growth conditions, but their amounts appeared adjusted to the requirements of peptidoglycan synthesis. Under the different in vitro conditions considered, only low levels of L-alanine adding activity were observed.