ENZYME CATALYSIS OF ELECTRON AND GROUP TRANSFER

这项拨款资助的研究的长远目标是 确定维生素B1的辅酶形成的化学机制 (硫胺素焦磷酸)和维生素B6(吡哆醛-5‘-磷酸，PLP) 在无法用传统机制解释的反应中起作用 以这些辅酶闻名。2-乙酰-TPP在人血清白蛋白代谢中的作用 丙酮酸脱氢酶(PDH)复合体催化的丙酮酸 用化学方法测定。丙酮酸的几种遗传性疾病 新陈代谢是由PDH复合体的缺陷引起的。标准 PLP辅酶作用的机械范式涉及 辅酶对碳离子中间体的稳定作用。但是，在一个 这笔赠款支持的主要研究重点是PLP在 赖氨酸2，3-氨基变位酶催化β-赖氨酸PLP的赖氨酸转化 建议通过稳定激进中间体来采取行动，而不是 Carbanion，.这是PLP与其他物质结合的一种新的化学机制。 氨基变位酶，如β-赖氨酸变位酶和精氨酸2，3-氨基变位酶。这个 氨基变位酶催化1，2-氨基迁移，这些迁移在 氨基酸代谢与霉素等抗生素的生物合成 和杀菌素I。由这笔赠款支持的研究将测试新的 应用光谱和化学的机理假说 方法：研究方法。氨基变位反应也与维生素B12有关；事实上 β-赖氨酸氨基变位酶是一种腺苷钴胺依赖酶。赖氨酸 2，3-氨基变位酶催化化学上类似的1，2-氨基 重排，但没有维生素B12辅酶，尽管有脂肪 活细胞中几乎所有这种化学类型的重排 将腺苷钴胺作为一种重要的辅酶。赖氨酸的辅因子 2，3-氨基变位酶为铁-硫簇、钴(II)和S- 腺苷蛋氨酸(ADOMet)。目前掌握的信息表明， ADOMet和金属辅因子通过化学作用生成腺苷- 一种化学性质与腺苷钴胺相同的辅因子。 由这笔赠款支持的研究将寻求通过以下方式来描述这种辅因 光谱和化学方法的应用。因此，中央 大多数研究的主旨是阐明新的化学机制。 维生素B1、B6和B12的辅酶形式的生物学作用。 最近产生的一个生物化学问题是确定化学物质 用遗传学方法发现和表征蛋白质的功能。一个 需要一种新的方法来识别这些蛋白质的内源性配体。 这种方法就是为此目的而开发的。

The long term objectives of the research supported by this grant are to determine the chemical mechanisms by which the coenzyme forms of vitamin B1 (thiamin pyrophosphate, TPP) and vitamin B6 (pyridoxal-5'-phosphate, PLP) act in reactions that cannot be explained by the conventional mechanisms known for these coenzyme. The role of 2-acetyl-TPP in the metabolism of pyruvate catalyzed by the pyruvate dehydrogenase (PDH) complex will be determined using chemical methods. Several inherited diseases of pyruvate metabolism are caused by defects in the PDH complex. The standard mechanistic paradigm for the coenzymatic action of PLP involves the stabilization of carbanionic intermediates by the coenzyme. However, in a major focus of research supported by this grant, the action of PLP in the lysine 2,3-aminomutase-catalyzed conversion of lysine of beta-lysine PLP is proposed to act by stabilizing a radical intermediate, rather than a carbanion,. This is a new chemical mechanism for PLP with other aminomutases, such as beta-lysine mutase and arginine 2,3,-aminomutase. The aminomutases catalyze 1,2-amino group migrations that are important in amino acid metabolism and the biosynthesis of antibiotics such as mycomycin and Blasticidin I. Research supported by this grant will test the new mechanistic hypothesis by application of spectroscopic and chemical methods. The aminomutase reactions are also related to vitamin B12; in fact beta-lysine aminomutase is an adenosylcobalamin-dependent enzyme. Lysine 2,3-aminomutase catalyzes a chemically similar 1,2-amino group rearrangement, but does so without a vitamin B12 coenzyme, despite the fat that nearly all rearrangements of this chemical type in living cells involve adenosylcobalamin as an essential coenzyme. The cofactors of lysine 2,3,-aminomutase are iron-sulfur cluster, cobalt(II) and S- adenosylmethionine (AdoMet). Currently available information indicates that AdoMet and the metal cofactors interact chemically to generate an adenosyl- cofactor that has chemical properties in common with adenosycobalamin.a The research supported by this grant will seek to characterize this cofactor by the application of spectroscopic and chemical methods. Thus the central thrust of most of research is the elucidation of new chemical mechanisms in the biological actions of the coenzymatic forms of vitamins B1,B6, and B12. A biochemical problem of recent origin is that of determining the chemical functions of proteins discovered and characterized by genetic methods. A new method for identifying endogenous ligands for such proteins is needed. Such method is being developed for this purposed.