Turker M S, Martin G M
Mol Cell Biol. 1985 Oct;5(10):2662-8. doi: 10.1128/mcb.5.10.2662-2668.1985.
Adenine phosphoribosyltransferase (APRT) (EC 2.4.2.7) pseudorevertant cell lines were isolated under selective conditions requiring adenine salvage for survival; yet they were found to be deficient in measurable APRT activity and resistant to the purine analog 2'6'-diaminopurine (DAP) (M.S. Turker, J. A. Tischfield, P. Rabinovitch, P.J. Stambrook, J.J. Trill, A.C. Smith, C.E. Ogburn, and G.M. Martin, manuscript in preparation). Adenine salvage was examined in two APRT pseudorevertant cell lines, their two APRT homozygous deficient parental cell lines, and a genotypic APRT revertant cell line (i.e., one with measurable APRT activity and DAP sensitivity). Adenine accumulation was observed in both revertant phenotypes and was demonstrated by high-performance liquid chromatography to be linked with adenine metabolism. The ability to salvage adenine declined substantially in the pseudorevertant cell lines when they were removed from selective media containing inhibitors of de novo 5'-AMP synthesis (alanosine and azaserine); for one pseudorevertant cell line this decline was accelerated by the addition of DAP to the medium. The readdition of alanosine or azaserine to the growth medium of the pseudorevertant lines induced adenine salvage to its previous levels. An APRT-like cross-reacting material was found in the pseudorevertant cell lines, although its relationship to adenine salvage is unknown. A low level of constitutive adenine salvage was found in the parental APRT-deficient lines, and it was also possible to induce adenine salvage in these cell lines. These findings suggest a novel regulatory mechanism for adenine salvage.
在需要腺嘌呤补救以维持生存的选择性条件下，分离出了腺嘌呤磷酸核糖转移酶（APRT）（EC 2.4.2.7）假回复细胞系；然而，发现它们缺乏可测量的APRT活性，并且对嘌呤类似物2'6'-二氨基嘌呤（DAP）具有抗性（M.S. 图尔克、J.A. 蒂施菲尔德、P. 拉比诺维奇、P.J. 斯坦布鲁克、J.J. 特里尔、A.C. 史密斯、C.E. 奥格本和G.M. 马丁，正在准备的手稿）。在两个APRT假回复细胞系、它们的两个APRT纯合缺陷亲本细胞系以及一个基因型APRT回复细胞系（即具有可测量的APRT活性和DAP敏感性的细胞系）中检测了腺嘌呤补救情况。在两种回复表型中均观察到腺嘌呤积累，并且通过高效液相色谱法证明其与腺嘌呤代谢有关。当从含有从头合成5'-AMP抑制剂（丙氨菌素和重氮丝氨酸）的选择性培养基中去除时，假回复细胞系中腺嘌呤补救能力大幅下降；对于一个假回复细胞系，向培养基中添加DAP会加速这种下降。向假回复细胞系的生长培养基中重新添加丙氨菌素或重氮丝氨酸可使腺嘌呤补救恢复到先前水平。在假回复细胞系中发现了一种类似APRT的交叉反应物质，尽管其与腺嘌呤补救的关系尚不清楚。在亲本APRT缺陷细胞系中发现了低水平的组成型腺嘌呤补救，并且也有可能在这些细胞系中诱导腺嘌呤补救。这些发现提示了一种腺嘌呤补救的新型调节机制。
