An alternate pathway to the glyoxylate cycle

植物和微生物能够仅用乙酰辅酶A合成所有细胞成分。乙醛酸循环是由Kornberg和Krebs在1957年发现的。异柠檬酸裂解酶（催化异柠檬酸裂解为琥珀酸和乙醛酸）和苹果酸合成酶（催化乙醛酸和乙酰辅酶A缩合形成苹果酸）是该中心代谢途径的关键酶。在过去的40年里，已经表明有生物体缺乏乙醛酸循环的关键酶和编码这些酶的基因。该提案的目标是阐明乙酰辅酶A同化的替代途径。以紫色非硫细菌球形红细菌为模式生物进行研究。生物体的基因组被测序。我们正在使用13 C-和14 C-示踪研究，突变体分析，酶活性的体外检测，蛋白质组学分析和比较基因组研究。我们希望进一步深入了解细菌的中心碳代谢。

Plants and microorganisms are capable to synthesize all cell constituents from acetyl-CoA alone. The glyoxylate cycle, discovered by Kornberg and Krebs in 1957, is used. Isocitrate lyase (catalyzing the cleavage of isocitrate to succinate and glyoxylate) and malate synthase (catalyzing the condensation of glyoxylate and acetyl-CoA to form malate) are the key enzymes of this central metabolic pathway. Over the last 40 years it has been shown that there are organisms, which lack the key enzymes of the glyoxylate cycle and the genes encoding these. The goal of this proposal is to elucidate an alternate pathway for acetyl-CoA assimilation. As a model organism we will study the purple non-sulfur bacterium Rhodobacter sphaeroides. The genome of the organism is sequenced. We are using 13C-and 14C-tracer studies, mutant analyses, in vitro detection of enzyme activities, proteomic analysis, and comparative genome studies. We expect to gain further inside into the central carbon metabolism of bacteria.