Iglehart J K, York R M, Modest A P, Lazarus H, Livingston D M
J Biol Chem. 1977 Oct 25;252(20):7184-91.
A number of continuous, human lymphoid cell lines from healthy and leukemic donors have been studied. Those from healthy individuals were found to be cystine prototrophs (cys+), while those from leukemic donors were observed to be cystine auxotrophs (cys-). The former can grow in either cystine or cystathionine-containing media. The latter grow only in cystine-containing medium. The former contain readily measurable levels of cystathionase, the last enzyme in the mammalian cysteine biosynthetic pathway, while the latter contain much less of this activity. The apparent molecular weight, overall charge, pH versus activity, Km, and [pyridoxal phosphate] versus activity properties of the enzyme from both cell types were indistinguishable. No soluble cystathionase inhibitor could be detected in cys- cell lines. Thus, it is reasonable to hypothesize that those leukemic cell lines studied synthesize less active cystathionase protein than their cys+ counterparts and that this difference in enzyme production underlies the differential growth properties in cystathionine-containing medium.
已经对来自健康供体和白血病供体的许多连续的人淋巴细胞系进行了研究。发现来自健康个体的细胞系是胱氨酸原养型（cys+），而来自白血病供体的细胞系则是胱氨酸营养缺陷型（cys-）。前者可以在含胱氨酸或含胱硫醚的培养基中生长。后者仅在含胱氨酸的培养基中生长。前者含有易于测量水平的胱硫醚酶，这是哺乳动物半胱氨酸生物合成途径中的最后一种酶，而后者含有少得多的这种活性。两种细胞类型的酶的表观分子量、总电荷、pH与活性、Km以及[磷酸吡哆醛]与活性特性没有区别。在cys-细胞系中未检测到可溶性胱硫醚酶抑制剂。因此，合理的假设是，所研究的那些白血病细胞系合成的活性胱硫醚酶蛋白比其cys+对应物少，并且这种酶产生的差异是含胱硫醚培养基中生长特性差异的基础。
