Biosynthesis Studies of Branched-Chain Amino Acids by Methanogenic Bacteria

乙酰羟酸合成酶（AHAS）是一种重要的调节酶 在支链氨基酸生物合成的途径中。 因为这些氨基酸占干重的25%， 活组织中蛋白质的重量，这一途径是 在许多微生物和植物中的数量意义。 产甲烷古细菌的AHAS 风状甲烷球菌正在按标准纯化 技术及其化学和物理性质 测定 这种酶的基因正在克隆， DNA测序开始。 一些主要问题是 通过这项研究解决。 合成代谢酶在 与真细菌和真核细菌同源的古细菌 酵素？ 古细菌AHAS是否与 在分解代谢途径中发现的代谢酶 包括大肠杆菌的丙酮酸氧化酶 是 AHAS中保守的黄素和除草剂结合位点 从不同的起源？ 产甲烷细菌是一个重要的经济类群 属于生命的第三大王国， 古细菌 它们催化厌氧消化的最后一步 分解有机物，其中95%的燃烧 能量保存在形成的甲烷中。 复杂 生物聚合物可以转化为甲烷，一种清洁燃料， 已经在广泛使用。 因此， 在废物处理中利用这种发酵。 此外，甲烷是第二丰富的碳- 大气中含有气体。 它的浓度一直是 在过去的几百年里， 导致温室效应和全球变暖。 因此 这些微生物与主要的 我们星球的全球进程。 这些关于产甲烷菌的研究 生理学和调节将促进它们的开发 用于有用的目的，并帮助衡量环境 实践。*/

Acetohydroxy acid synthase (AHAS) is a key regulatory enzyme in the pathway of branched-chain amino acid biosynthesis. Because these amino acids constitute about 25% of the dry weight of protein in living tissue, this pathway is of quantitative significance in many microorganisms and plants. The AHAS from a methane-producing archaebacterium, Methanococcus aeolicus, is being purified by standard techniques, and its chemical and physical properties determined. The gene(s) for this enzyme is being cloned and DNA sequencing begun. A number of major questions are addressed by this research. Are anabolic enzymes in archaebacteria homologous to the eubacterial and eucaryotic enzymes? Is the archaebacterial AHAS homologous to any pyruvate-utilizing enzymes found in catabolic pathways including the pyruvate oxidase from Escherichia coli? Are the flavin and herbicide binding sites conserved in AHASs from diverse origins?%%% Methanogenic bacteria are an economically important group belonging to the third major kingdom of life, the archaebacteria. They catalyze the last step in the anaerobic decomposition of organic matter where 95% of the combustion energy is conserved in the methane formed. Complex biological polymers can be converted to methane, a clean fuel already in wide use. Therefore, there is great potential for exploitation of this fermentation in waste treatment. Furthermore, methane is the second most abundant carbon- containing gas in the atmosphere. Its concentration has been increasing for the last several hundred years and may contribute to the greenhouse effect and global warming. Thus these microorganisms are intimately associated with major global processes of our planet. These studies on methanogen physiology and regulation will facilitate their exploitation for useful purposes and help gauge environmental practices.***//