Stern E S, Krooth R S
J Cell Physiol. 1975 Aug;86(1):91-104. doi: 10.1002/jcp.1040860111.
In human diploid cell strains, the substitution of galactose for glucose as the sole hexose in the medium had no measurable effect on the specific activity of the cell protein for any of the three enzymes of the Leloir pathway. These enzymes are galactokinase, alpha-D-galactose-1-phosphate: UDP glucose uridyl transferase and UDP galactose 4-epimerase. A cell strain from a patient with galactosemia had no detectable activity for the transferase. The substitution of galactose for glucose in the medium of these cells (which has been shown to cause the cells to accumulate galactose-1-phosphate) also failed to affect cellular activity for the three enzymes. Similarly, the three activities failed to respond to the substitution of galactose for glucose in cultures of a rat hepatoma line. Cells of this line have been shown by others to perform a number of the tissue-specific functions of liver. The failure of galactose to stimulate increasd cellular activity for the three enzymes represents a striking difference between the behavior of these enzymes in human diploid cell strains and their behavior in E. coli.
在人二倍体细胞株中，用半乳糖替代葡萄糖作为培养基中唯一的己糖，对Leloir途径的三种酶中任何一种酶的细胞蛋白比活性都没有可测量的影响。这些酶是半乳糖激酶、α-D-半乳糖-1-磷酸：UDP葡萄糖尿苷酰转移酶和UDP半乳糖4-差向异构酶。来自半乳糖血症患者的细胞株中转移酶没有可检测到的活性。在这些细胞的培养基中用半乳糖替代葡萄糖（已证明会导致细胞积累半乳糖-1-磷酸）也未能影响这三种酶的细胞活性。同样，在大鼠肝癌细胞系培养物中，这三种活性也未对用半乳糖替代葡萄糖作出反应。其他人已表明该细胞系的细胞具有肝脏的许多组织特异性功能。半乳糖未能刺激这三种酶的细胞活性增加，这代表了这些酶在人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。
