carboxylaationen

Carboxylation, also encountered as carboxylationen in German-language texts, is the introduction of a carboxyl group (-COOH) into an organic substrate or the fixation of carbon dioxide into organic molecules. It occurs in two broad contexts: enzymatic processes in living systems and chemical synthesis in the laboratory. Enzymatic carboxylation typically uses CO2 or bicarbonate as the carbon source and requires energy input and cofactors such as ATP and biotin or biotin-dependent enzymes.

Biological examples include photosynthetic carbon fixation by RuBisCO, which carboxylates ribulose-1,5-bisphosphate with CO2 to produce two molecules of 3-phosphoglycerate, a step in the Calvin cycle. In metabolism, pyruvate carboxylase forms oxaloacetate from pyruvate, supporting replenishment of TCA cycle intermediates. Acetyl-CoA carboxylase carboxylates acetyl-CoA to malonyl-CoA, the first committed step in fatty acid synthesis. Propionyl-CoA carboxylase generates methylmalonyl-CoA, contributing to odd-chain fatty acid metabolism and biotin-dependent pathways.

Chemical carboxylation methods insert carboxyl groups into substrates using CO2 or bicarbonate, often under catalysis by transition metals or organocatalysts. Classic demonstrations include reaction of organolithium or Grignard reagents with CO2 to yield carboxylic acids after workup. More advanced methods use metal catalysts to enable carboxylation of aryl or alkenyl substrates with CO2, providing a route to carboxylated products. In industry, carboxylation and CO2 fixation are central to carbon capture and utilization strategies, linking chemical synthesis to sustainability goals.