Whitfield C D, Buchsbaum B, Bostedor R, Chu E H
Somatic Cell Genet. 1978 Nov;4(6):699-713. doi: 10.1007/BF01543159.
Galactokinase activity is reduced in 12 independent clones of Chinese hamster ovary cells resistant to 2-deoxygalactose. The frequency of resistant colonies is increased with chemical mutagens. The resistant phenotype is stable in the absence of selection. There is an inverse correlation between the levels of galactokinase activity and the cloning efficiency in deoxygalactose. Cells with high resistance have 1% or less of the enzyme activity observed in the parental cells; while cells with low resistance have 10-30% galactokinase activity. Studies with tetraploid hybrid cells reveal that resistance to deoxygalactose is a recessive trait and that cells with high resistance do not complement those with low resistance. In cell lines with low resistance, the Km for galactose, Ki for deoxygalactose, Km for ATP, and thermolability were not significantly altered compared to sensitive parental cells. Although the possibility of mutation at the structural gene locus has not been ruled out, the reduced enzyme activity may also be due to mutation at a regulatory site which affects the number of galactokinase molecules per cell.
在对2-脱氧半乳糖具有抗性的12个独立的中国仓鼠卵巢细胞克隆中，半乳糖激酶活性降低。用化学诱变剂可增加抗性菌落的频率。在无选择的情况下，抗性表型是稳定的。在脱氧半乳糖中，半乳糖激酶活性水平与克隆效率之间呈负相关。高抗性细胞的酶活性仅为亲代细胞的1%或更低；而低抗性细胞具有10 - 30%的半乳糖激酶活性。对四倍体杂交细胞的研究表明，对脱氧半乳糖的抗性是一种隐性性状，高抗性细胞不能与低抗性细胞互补。在低抗性细胞系中，与敏感的亲代细胞相比，半乳糖的Km值、脱氧半乳糖的Ki值、ATP的Km值以及热稳定性均无显著改变。尽管尚未排除结构基因位点发生突变的可能性，但酶活性降低也可能是由于影响每个细胞中半乳糖激酶分子数量的调控位点发生了突变。
