Asetüülkoensüüm

Asetüülkoensüüm A, often abbreviated as asetüül-CoA, is a crucial molecule in metabolism. It is a thioester of coenzyme A and acetic acid. Its primary role is to deliver the acetyl group to the citric acid cycle (also known as the Krebs cycle) to fuel cellular respiration. This acetyl group is derived from the breakdown of carbohydrates, fats, and proteins.

Asetüül-CoA is formed through several metabolic pathways. The most prominent is the conversion of pyruvate, the end product of glycolysis, by the pyruvate dehydrogenase complex. Fatty acids are broken down into acetyl-CoA units through beta-oxidation. Amino acids can also be catabolized to produce acetyl-CoA, either directly or indirectly through intermediates of the citric acid cycle.

Once formed, acetyl-CoA enters the citric acid cycle, where its acetyl group is oxidized, generating ATP (adenosine triphosphate), the cell's main energy currency, along with reduced electron carriers like NADH and FADH2. These carriers then proceed to the electron transport chain to produce even more ATP.

Beyond its role in energy production, acetyl-CoA is also a precursor for various biosynthetic pathways. It is essential for the synthesis of fatty acids, cholesterol, and ketone bodies. The balance of acetyl-CoA levels is tightly regulated to meet the cell's energy demands and supply building blocks for essential molecules.