Unfamiliar metabolic links in the central carbon metabolism

作者：Fuchs Georg; Berg Ivan A^*

来源：Journal of Biotechnology, 2014, 192: 314-322.

DOI：10.1016/j.jbiotec.2014.02.015

• Autotrophic CO2 fixation
• Acetyl-CoA assimilation
• 3-Hydroxypropionate
• 4-Hydroxybutyrate
• C-5 dicarboxylic acids

The central carbon metabolism of all organisms is considered to follow a well established fixed scheme. However, recent studies of autotrophic carbon fixation in prokaryotes revealed unfamiliar metabolic links. A new route interconnects acetyl-coenzyme A (CoA) via 3-hydroxypropionate with succinyl-CoA. Succinyl-CoA in turn may be metabolized via 4-hydroxybutyrate to two molecules of acetyl-CoA; a reversal of this route would result in the assimilation of two molecules of acetyl-CoA into C-4 compounds. C-5-dicarboxylic acids are a rather neglected class of metabolites; yet, they play a key role not only in one of the CO2 fixation cycles, but also in two acetate assimilation pathways that replace the glyoxylate cycle. C-5 compounds such as ethylmalonate, methylsuccinate, methylmalate, mesaconate, itaconate and citramalate or their CoA esters are thereby linked to the acetyl-CoA, propionyl-CoA, glyoxylate and pyruvate pools. A novel carboxylase/reductase converts crotonyl-CoA into ethylmalonyl-CoA; similar reductive carboxylations apply to other alpha-beta-unsaturated carboxy-CoA thioesters. These unfamiliar metabolic links may provide useful tools for metabolic engineering.

• 出版日期2014-12-20