FOLYL POLYGLUTAMATES AND FOLATE-DEPENDENT ENZYMES

目前我们仅掌握有限的信息 叶酰聚谷氨酸的链长用于引导 哺乳动物细胞中通过竞争途径形成一个碳单位。 的 本文所述的研究旨在提供有关 各种叶酸依赖性酶的特异性 叶酸共底物的聚谷氨酸“尾部”中的谷氨酰残基和 抑制剂。 此类研究可用于预测代谢通量的模式 对于不同聚谷氨酸链长度的叶酸衍生物。 他们是 也可用于预测临床上多聚谷氨酰化的效果 重要的抗叶酸药物，例如甲氨蝶呤，对多种 叶酸依赖性反应。 此外，我们相信 叶酰聚谷氨酸底物可能在机械研究中非常有用， 特别是当它们导致添加顺序发生变化时 底物与单谷氨酸观察到的添加顺序相比 叶酸底物。 在本提案中，我们计划继续我们的 检查叶酰聚谷氨酸盐与 使用稳态动力学组合的叶酸依赖性酶 研究和结构研究。 我们将继续研究 亚甲基四氢叶酸脱氢酶、胸苷酸合成酶、丝氨酸 羟甲基转移酶和亚甲基四氢叶酸还原酶，并且将 启动AICAR和GAR转化酶和蛋氨酸合酶的研究。

At present we have only limited information available on the extent to which the chain length of folylpolyglutamates serves to direct the flux of one carbon units through competing pathways in mammalian cells. The studies described herein are aimed at providing basic information on the specificities of various folate-dependent enzymes for the number of glutamyl residues in the polyglutamate "tail" of folate cosubstrates and inhibitors. Such studies can be used to predict patterns of metabolic flux for folate derivatives of differing polyglutamate chain length. They are also useful for predicting the effect of polyglutamylation of clinically important antifolate drugs such as methotrexate on the various folate-dependent reactions. In addition, we believe that folylpolyglutamate substrates may prove very useful in mechanistic studies, particularly where they lead to changes in the order of addition of substrates as compared to the order of addition observed with monoglutamate folate substrate. In the present proposal we plan to continue our examination of the interactions of folylpolyglutamates with folate-dependent enzymes using a combination of steady-state kinetic studies and structural studies. We will continue studies on methylenetetrahydrofolate dehydrogenase, thymidylate synthase, serine hydroxymethyl-transferase and methylenetetrahydrofolate reductase, and will initiate studies on AICAR and GAR transformylase and methionine synthase.