An alternate pathway to the glyoxylate cycle

植物和微生物能够仅由乙酰辅酶a合成所有细胞成分。使用了Kornberg和Krebs在1957年发现的乙醛酸循环。异柠檬酸裂解酶（催化异柠檬酸裂解成琥珀酸盐和乙醛酸盐）和苹果酸合成酶（催化乙醛酸盐和乙酰辅酶a缩合成苹果酸盐）是这一中心代谢途径的关键酶。在过去的40年里，已经证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。本提案的目的是阐明乙酰辅酶a同化的另一途径。作为一种模式生物，我们将研究紫色非硫细菌球形红杆菌。生物体的基因组被测序。我们正在使用13c和14c示踪研究、突变分析、体外酶活性检测、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核心碳代谢。

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.