MECHANISM OF AUTOTROPHIC GROWTH WITH CO OR C02 AND H2

乙酰辅酶A的合成机制已部分阐明 和来自甲基四氢叶酸（CH3THF）的乙酰磷酸盐，一氧化碳 (CO)、辅酶A（CoASH）和磷酸盐，通过使用来自梭菌属的酶 热醋酸。 该机制涉及甲基基团从 CH3THF与含柯啉（维生素B12）的酶的钴反应。 的 CO通过镍酶CO脱氢酶转化为C1中间体。 这种C1中间体与CoASH一起，通过一种机制， 未知，与类可丽素的甲基结合形成乙酰辅酶A。 ATP 是必需的. CO2和H2可以代替CO作为C1的来源， 中间体 在这种情况下，CO2被还原为C1中间体 利用氢酶产生的电子。 这些 反应是特别感兴趣的，因为它们可以提供一种机制， 某些细菌以CO或CO2和H2为碳源生长 和能量。 本研究的目的是：（1）分离和 纯化催化这一系列反应的酶;（2） 分离反应中发生的中间体化合物，并探索 反应机制;（3）进行自养研究 以确定它们是否利用这种机制。 放射性示踪剂和13C-核磁共振将用于 检测中间化合物。 一氧化碳是有毒气体， 由化石燃料的燃烧和其他 流程. 细菌通过CO脱氢酶从大气中去除CO， 有助于保持大气浓度非常低。 阐发 金属钴镍和维生素 B12在CO和CO2和H2转化为乙酸的酶中的功能 将提供至关重要的基础知识。 在未来当 油成为限制，发酵产乙酸细菌使用CO和 CO2和H2可以作为乙酸的来源得到技术应用， 合成过程。

A mechanism has been partially elucidated for the synthesis of acetyl-CoA and acetylphosphate from methyltetrahydrofolate (CH3THF), carbon monoxide (CO), coenzyme A (CoASH), and phosphate by use of enzymes from Clostridium thermoaceticum. The mechanism involves transfer of the methyl group from CH3THF to the cobalt of a corrinoid (vitamin B12) containing enzyme. The CO is converted to a C1 intermediate by a nickel enzyme, CO dehydrogenase. This C1 intermediate together with CoASH, by a mechanism which is as yet unknown, combines with the methyl of the corrinoid to form acetyl-CoA. ATP is required. CO2 and H2 can be substituted for CO as the source of the C1 intermediate. In this case, the CO2 is reduced to the C1 intermediate using electrons generated from the H2 by the enzyme, hydrogenase. These reactions are of particular interest since they may provide a mechanism by which certain bacteria grow with CO or CO2 and H2 as the source of carbon and energy. The objectives of this investigation are: (1) to isolate and purify the enzymes which catalyze this sequence of reactions; (2) to isolate intermediate compounds which occur in the reactions and explore the mechanisms of the reactions; (3) to conduct studies with autotrophic organisms to determine whether or not they utilize this mechanism. Radioactive tracers and 13C-nuclear magnetic resonance will be used in detecting intermediate compounds. Carbon monoxide is a toxic gas which is formed in large quantities by the combustion of fossil fuels and by other processes. Bacteria via CO dehydrogenase remove CO from the atmosphere and assist in maintaining the atmospheric concentration very low. Elucidation of the biochemical reactions by which the metals cobalt, nickel and vitamin B12 function in enzymes in the conversion of CO and CO2 and H2 to acetate will provide basic knowledge of fundamental importance. In the future when oil becomes limiting, the fermentation by acetogenic bacteria using CO and CO2 and H2 may find technical application as a source of acetic acid for synthetic processes.