STRUCTURAL STUDIES OF METHYL CYCLE ENZYMES

S-腺苷蛋氨酸(ADOMet)介导的甲基化反应 越来越多地被认为是 调节多种细胞功能。核酸的甲基化是 已知对DNA复制和转录有调节作用，以及RNA 翻译。蛋白质甲基化参与调节多种 代谢过程，如细菌趋化性，精子流动性，释放 神经递质，可能还有某些酶活性。ADOMet也是 大量小分子的甲基供体(例如，生物合成 和/或各种儿茶酚胺神经递质的代谢)。 我们已经研究了参与的酶的结构和功能 甲基循环反应。一个相对较大的构象变化是 在底物结合或离开时在酶结构中观察到 来自活动站点的产品。在这一资助期内，高佐川博士将 表征分子的动态结构和催化机理 用X-射线衍射法对酶进行跟踪。 人、大鼠、詹氏甲烷球菌和金黄色葡萄球菌的S-腺苷乙硫氨酸合成酶 大肠埃希菌。大鼠Glycline N-甲基转移酶和乙酸胍甲基转移酶 肝脏。S-大鼠肝脏和粪产碱菌的腺苷同型半胱氨酸水解酶。 大肠埃希菌S腺苷蛋氨酸脱羧酶。N10-甲酰-四氢叶酸合成酶 来自柱状芽孢梭菌。大鼠肝脏丝氨酸脱水酶。 为了长期目标，我们希望设计特定的抑制剂。 以开发使用这些酶的化疗药物 得到的酶的活性中心几何构型和催化机理 在这个项目中。

Methylation reactions mediated by S-adenosylmethlonine (AdoMet) are increasingly being recognized as significant control factors in the regulation of a variety of cellular functions. Methylation of nucleic acids is known to have regulatory effects on DNA replication and transcription, and RNA translation. Protein methylation is involved in the regulation of a variety of metabolic processes such as bacterial chemotaxis, sperm mobility, release of neurotransmitters and possibly certain enzymatic activities. AdoMet is also the methyl donor for a vast number of small molecules (e.g., the biosynthesis and/or metabolism of various catechoiamine neurotransmitters). We have studied the structures and functions of enzymes involved in the methyl cycle reactions. A relatively large conformational change has been observed in the enzyme structures upon the binding of substrate or the leaving of product from the active site. In this grant period, Dr. Takusagawa will characterize the dynamic structures as well as the catalytic mechanisms of the following enzymes by X-ray diffraction method. S-adenosylm ethionine synthetase from human, rat, Methanococcus jannaschii, and E. coli. Glycline N-methyltransferase and guanidinoacetate methyltransferase from rat liver. S-adenosylhomocysteine hydrolase from rat liver and Alcaligenes faecalis. S-adenosylmethionine decarboxylase from E. coli. N10-formyl-tetrahydrofolate synthetase from Clostridium cylindrosporum. Serine dehydratase from rat liver. For a long-term objective, we would like to design specific inhibitors of these enzymes in order to develop chemotherapeutic agents using the active site geometries and the catalytic mechanisms of the enzymes gained in this project.