karboksülaatse

Karboksülaatse is a class of enzymes that catalyze the addition of carbon dioxide (CO2) to various substrates. This reaction is known as carboxylation. Carboxylation is a fundamental process in many biological pathways, including photosynthesis, fatty acid synthesis, and the urea cycle. These enzymes play a crucial role in carbon fixation, a process that converts inorganic carbon dioxide into organic compounds.

The mechanism of action for carboxylases typically involves the activation of CO2, often by binding to a metal ion cofactor, such as magnesium (Mg2+) or manganese (Mn2+), which is usually coordinated by the enzyme's active site. This activated CO2 then reacts with the substrate. Carboxylation reactions are often endergonic (require energy input), and this energy is usually supplied by the hydrolysis of adenosine triphosphate (ATP).

A well-known example of a carboxylase is RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase), a key enzyme in the Calvin cycle of photosynthesis. RuBisCO catalyzes the first major step in carbon fixation, incorporating atmospheric CO2 into an organic molecule. Another important carboxylase is acetyl-CoA carboxylase (ACC), which catalyzes the synthesis of malonyl-CoA, a crucial intermediate in fatty acid biosynthesis. Different carboxylases have distinct substrate specificities and biological functions, highlighting their diverse roles in metabolism.