REGULATION OF PHOSPHOLIPID SYNTHESIS BY CTP

在酿酒酵母中，CTP、CTP合成酶反应 产品是磷脂的前体，由 CDP-二酰甘油和肯尼迪(CDP-胆碱)途径以及ALL 膜磷脂。在本期拨款期间进行的研究 期间显示CTP合成酶活性在体内起调节作用 用于合成的途径的利用 卵磷脂。对CTP合成酶进行了纯化、鉴定和鉴定。 被证明通过蛋白激酶A的磷酸化而被激活 蛋白激酶C，并被CTP抑制。在这场竞争的延续中 资助申请我们建议进行分子遗传学和生物化学研究 预计将为CTP的监管提供洞察 通过磷酸化和CTP产物抑制合成酶活性以及 这一规定与以下方面的生理相关性 磷脂合成。他们建议检验这样一种假设，即 通过磷酸化调节CTP合成酶活性涉及 该酶的核苷酸依赖的四聚反应。CTP合成酶 突变株将用改变的蛋白激酶A和蛋白质分离 蛋白激酶C的磷酸化位点。这些突变体将被用于 生理和生化研究，以检查影响 磷酸化对CTP合成酶活性的调节。这个 这一磷脂合成调节的影响将被提出 分离在CTP中建议的CTP结合部位有缺陷的突变体 合成酶。这些突变体将用于生理学和 CTP合成酶调控的生物化学研究 活性受CTP产物抑制。这一规定对 将考察磷脂的合成。建议的结果 研究应与高等真核生物相关，并应 对其他调查人员的工作非常感兴趣，并对其进行补充 磷脂代谢领域。这项工作也应该是相关的 到依赖于CTP的大分子合成的其他方面 作为前兆。

In the yeast Saccharomyces cerevisiae, CTP, the CTP synthetase reaction product, is a precursor of phospholipids that are synthesized by the CDP-diacylglycerol and Kennedy (CDP-choline) pathways as well as all membrane phospholipids. Studies performed during the current grant period showed that CTP synthetase activity plays a regulatory role in the utilization of the pathways used for the synthesis of phosphatidylcholine. CTP synthetase was purified, characterized, and shown to be activated by phosphorylation via protein kinase A and protein kinase C and inhibited by CTP. In this competitive continuation grant application we propose molecular genetic and biochemical studies that are expected to provide insight into the regulation of CTP synthetase activity by phosphorylation and by CTP product inhibition and into the physiological relevance of this regulation with respect to phospholipid synthesis. They propose to examine the hypothesis that the regulation of CTP synthetase activity by phosphorylation involves the nucleotide-dependent tetramerization of the enzyme. CTP synthetase mutants will be isolated with altered protein kinase A and protein kinase C phosphorylation sites. These mutants will be used for physiological and biochemical studies to examine the effects of phosphorylation on the regulation of CTP synthetase activity. The effects of this regulation of phospholipid synthesis will be propose to isolate mutants that are defective in a proposed CTP binding site in CTP synthetase. These mutants will be used for physiological and biuochemical studies to examine the regulation of CTP synthetase activity by CTP product inhibition. The effect of this regulation on phospholipid synthesis will be examined. The results from the proposed studies should be relevant to higher eukaryotic organisms and be of great interest to, and complement the work of, other investigators in the field of phospholipid metabolism. This work should also be relevant to other aspects of macromolecular synthesis that are dependent on CTP as a precursor.