FOLYL POLYGLUTAMATES AND FOLATE-DEPENDENT ENZYMES

目前，我们只有有限的信息， 其中叶酰聚谷氨酸盐的链长用于引导 一个碳单位通过竞争途径在哺乳动物细胞。 的 本文所述的研究旨在提供有关 各种叶酸依赖酶的特异性， 叶酸辅助底物的聚谷氨酸"尾"中的谷氨酰残基， 抑制剂的 这样的研究可以用来预测代谢流的模式 对于不同聚谷氨酸盐链长的叶酸盐衍生物。 他们是 也可用于预测临床上的多聚谷氨酰化的作用， 重要的抗叶酸药物，如甲氨蝶呤对各种 叶酸依赖性反应 此外，我们认为， 叶酰聚谷氨酸底物可以证明在机理研究中非常有用， 特别是当它们导致添加顺序的改变时， 与单谷氨酸盐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 叶酸依赖性酶使用稳态动力学 研究和结构研究。 我们会继续研究 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，并将 启动AICAR和GAR转化酶和甲硫氨酸合酶研究。

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.