Alleman M M, Gottlieb M
Department of Molecular Microbiology and Immunology, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205, USA.
Mol Biochem Parasitol. 1996 Feb-Mar;76(1-2):279-87. doi: 10.1016/0166-6851(96)02566-2.
The effects of purine starvation on the ability of the trypanosomatid Crithidia luciliae to accumulate purines were determined. Kinetic studies showed that the uptake of the nucleoside adenosine by purine-starved organisms was approximately 7-fold faster than by nutrient-replete cells. Further, these studies demonstrated that purine-starved organisms accumulated the nucleobases hypoxanthine and adenine at a rate > 100-fold faster than organisms cultivated under replete conditions. Activities of several intracellular purine-salvage enzymes were measured in organisms from both culture conditions. Of those measured, the activities of adenine deaminase and hypoxanthine phosphoribosyltransferase were elevated approximately 4-fold and approximately 11-fold, respectively, in purine-starved organisms. Competitive substrate specificity studies suggested that these elevated enzyme activities were not responsible for the increased rates of uptake by purine-starved cells. The results are consistent with the induction of novel surface membrane purine transporters expressed in response to purine starvation. These studies using C. luciliae may provide insights into the mechanisms of trypanosomatid adaptation to altered environments encountered during the course of the life cycle.
研究了嘌呤饥饿对锥虫类鲁氏克氏锥虫积累嘌呤能力的影响。动力学研究表明，嘌呤饥饿的生物体对核苷腺苷的摄取速度比营养充足的细胞快约7倍。此外，这些研究表明，嘌呤饥饿的生物体积累嘌呤碱次黄嘌呤和腺嘌呤的速度比在充足条件下培养的生物体快100倍以上。在两种培养条件下的生物体中测量了几种细胞内嘌呤补救酶的活性。在所测量的酶中，嘌呤饥饿的生物体中腺嘌呤脱氨酶和次黄嘌呤磷酸核糖基转移酶的活性分别升高了约4倍和约11倍。竞争性底物特异性研究表明，这些升高的酶活性与嘌呤饥饿细胞摄取率的增加无关。结果与响应嘌呤饥饿而表达的新型表面膜嘌呤转运蛋白的诱导一致。这些使用鲁氏克氏锥虫的研究可能为锥虫适应生命周期中遇到的环境变化的机制提供见解。
