Acetoacetat

Acetoacetat, also called acetoacetate, is the conjugate base of acetoacetic acid and one of the ketone bodies produced during fatty acid metabolism. It is a four-carbon, beta-keto carboxylate that circulates in the blood in its ionized form at physiological pH.

In humans, ketone bodies are primarily formed in the liver during periods of fasting, prolonged exercise, or carbohydrate restriction. Fatty acids are oxidized to acetyl-CoA, which is then used to generate acetoacetyl-CoA and, through additional steps in hepatic mitochondria, ultimately acetoacetate and beta-hydroxybutyrate. These ketone bodies are released into the bloodstream and transported to extrahepatic tissues.

Utilization of acetoacetat occurs mainly in peripheral tissues such as muscle and brain. There, acetoacetate is activated to acetoacetyl-CoA by the enzyme succinyl-CoA: acetoacetate transferase (SCOT) using succinyl-CoA as a co-substrate. Acetoacetyl-CoA is then cleaved by thiolase to yield two acetyl-CoA molecules, which enter the citric acid cycle to generate energy.

Clinical relevance of acetoacetat lies with its role as a major ketone body. Increased levels occur during ketosis, such as prolonged fasting or adherence to a ketogenic diet; markedly elevated ketone bodies, including acetoacetate, are observed in diabetic ketoacidosis. Ketone body concentrations can be measured in blood or urine and are used to monitor metabolic states and related disorders.