Stern E S, Krooth R S
J Cell Physiol. 1975 Aug;86(1):105-10. doi: 10.1002/jcp.1040860112.
Studies on a normal human diploid cell strain revealed that the specific activity of the cell protein, for each of the three enzymes of the Leloir pathway, changed significantly as the cells grew. The kinetics of change in specific activity varied according to the enzyme being studied, and the kinetics for each enzyme varied from experiment to experiment. Within each experiment, there was no consistent correlation between specific activity for any one enzyme and specific activity for the other two. The ratios between the specific activities did not tend to remain constant as the absolute levels of specific activity changed. Hence, the activities did not behave coordinately. The kinetics of change in these ratios varied from experiment to experiment. The failure of galactose to stimulate increased cellular activity for the three enzymes (shown in the preceding paper), and the absence of a coordinate relationship between the activities, represent a striking difference between the behavior of these enzymes in human diploid cell strains and their behavior in E. coli.
对一种正常人类二倍体细胞株的研究表明，随着细胞生长，对于Leloir途径的三种酶中的每一种，细胞蛋白的比活性都发生了显著变化。比活性变化的动力学根据所研究的酶而有所不同，并且每种酶的动力学在不同实验中也有所不同。在每个实验中，任何一种酶的比活性与其他两种酶的比活性之间都没有一致的相关性。随着比活性的绝对水平发生变化，比活性之间的比率并不倾向于保持恒定。因此，这些活性并非协同表现。这些比率变化的动力学在不同实验中也有所不同。半乳糖未能刺激这三种酶的细胞活性增加（如前文所示），以及活性之间不存在协同关系，这代表了这些酶在人类二倍体细胞株中的行为与其在大肠杆菌中的行为之间的显著差异。
