Acetone carboxylation as a model reaction for anaerobic activation of hydrocarbons

在过去的资助期内，几种硝酸盐还原细菌的丙酮羧化酶与好氧细菌的丙酮羧化酶相似，即丙酮羧化为乙酰乙酸需要2个ATP当量。从丙酮为唯一底物的产甲烷富集培养物中分离出丙酮发酵菌，并将其归属于与D. orientis密切相关的Desulfosporosinus属。利用硫酸盐还原菌Desulfococcus biacutus，获得了一种新型丙酮活化的有力证据，其中丙酮与CO羰基化形成乙酰乙醛。在即将到来的资助期内，将对这种新型的“丙酮羰化”进行详细的研究。必须确定反应伙伴，富集和纯化所涉及的酶，并通过特异性表达蛋白的蛋白质组学和基因组分析来确定其遗传编码。整个反应链将通过酶的测量来阐明，并且类似的研究将扩展到Desulfobacterium cetonicum和最近分离的Desulfosporosinus sp。

In the past funding period, acetone carboxylases of several nitrate-reducing bacteria turned out to be similar to those of aerobic bacteria, i.e., they require 2 ATP equivalents for acetone carboxylation to acetoacetate. From methanogenic enrichment cultures with acetone as sole substrate, acetone-fermenting bacteria were isolated and assigned to the genus Desulfosporosinus, closely related to D. orientis. With the sulfate-reducing bacterium Desulfococcus biacutus, strong evidence for a novel type of acetone activation was obtained in which acetone is carbonylated with CO to form acetoacetaldehyde. In the upcoming funding period, this new type of “acetone carbonylation” is to be studied in detail. The reaction partners have to be identified, the involved enzyme(s) to be enriched and purified, and its genetic coding to be identified via proteomic and genomic analysis of specifically expressed proteins. The entire reaction chain is to be elucidated by enzyme measurements with respect to the overall energy balance of this metabolism, and similar studies are to be extended to Desulfobacterium cetonicum and the recently isolated Desulfosporosinus sp.