Acetoacetate decarboxylase
Encyclopedia
Activity in bacteria
In certain bacteria, acetoacetate decarboxylase is involved in solventogenesis, a process by which the butyric and acetic acid products of classical sugar fermentation are oxidized into acetone and butanol. The production of acetone by acetoacetate decarboxylase containing bacteria was utilized in large-scale industrial syntheses in the first half of the twentieth century. In the 1960s, the industry replaced this process with more efficient chemical syntheses of acetone.Acetoacetate decarboxylase has been found and studied in the following bacteria:
- Bacillus polymyxa
- Chromobacterium violaceumChromobacterium violaceumChromobacterium violaceum is a Gram-negative, facultative anaerobic, non-sporing coccobacillus. It is part of the normal flora of water and soil of tropical and sub-tropical regions of the world. It produces a natural antibiotic called violacein, which may be useful for the treatment of colon and...
- Clostridium acetobutylicumClostridium acetobutylicumClostridium acetobutylicum, ATCC 824, is included in the genus Clostridium, is a commercially valuable bacterium sometimes called the "Weizmann Organism", after Jewish-Russian born Chaim Weizmann, then senior lecturer at the University of Manchester, England, used them in 1916 as a bio-chemical...
- Clostridium beijerinckiiClostridium beijerinckiiClostridium beijerinckii is a gram positive, rod shaped, motile bacterium of the genus Clostridium. It has been isolated from feces and soil...
- Clostridium cellulolyticumClostridium cellulolyticumClostridium cellulolyticum is an anaerobic, motile, gram-positive bacterium....
- Pseudomonas putidaPseudomonas putidaPseudomonas putida is a gram-negative rod-shaped saprotrophic soil bacterium. Based on 16S rRNA analysis, P. putida has been placed in the P. putida group, to which it lends its name....
Activity in humans and mammals
While this enzyme has not been purified from human tissue, the activity was shown to be present in human blood serum.In humans and other mammals, the conversion of acetoacetate into acetone and carbon dioxide by acetoacetate decarboxylase is a final irreversible step in the ketone-body pathway that supplies the body with a secondary source of energy. In the liver, acetyl co-A formed from fats and lipids are transformed into three ketone bodies: acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
, acetoacetate, and D-β-hydroxybutyrate. Acetoacetate and D-β-hydroxybutyrate are exported to non-hepatic tissues, where they are converted back into acetyl-coA and used for fuel. Acetone and carbon dioxide on the other hand are exhaled, and not allowed to accumulate under normal conditions.
Acetoacetate and D-β-hydroxybutyrate freely interconvert through the action of D-β-hydroxybutyrate dehydrogenase. Subsequently, one function of acetoacetate decarboxylase may be to regulate the concentrations of the other, two 4-carbon ketone bodies.
Clinical significance
Ketone body production increases significantly when the rate of glucose metabolism is insufficient in meeting the body's energy needs. Such conditions include high-fat ketogenic diets, diabetic ketoacidosisDiabetic ketoacidosis
Diabetic ketoacidosis is a potentially life-threatening complication in patients with diabetes mellitus. It happens predominantly in those with type 1 diabetes, but it can occur in those with type 2 diabetes under certain circumstances...
, or severe starvation.
Under elevated levels of acetoacetate and D-β-hydroxybutyrate, acetoacetate decarboxylase produces significantly more acetone. Acetone is toxic, and can accumulate in the body under these conditions. Elevated levels of acetone in the human breath can be used to diagnose diabetes.