Ketoleucine (BioDeep_00000003211)

描述信息

Ketoleucine is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. Ketoleucine is both a neurotoxin and a metabotoxin. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of ketoleucine are associated with maple syrup urine disease (MSUD). MSUD is a metabolic disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), leading to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products (ketoacids) in the blood and urine. The symptoms of MSUD often show in infancy and lead to severe brain damage if untreated. MSUD may also present later depending on the severity of the disease. If left untreated in older individuals, during times of metabolic crisis, symptoms of the condition include uncharacteristically inappropriate, extreme, or erratic behaviour and moods, hallucinations, anorexia, weight loss, anemia, diarrhea, vomiting, dehydration, lethargy, oscillating hypertonia and hypotonia, ataxia, seizures, hypoglycemia, ketoacidosis, opisthotonus, pancreatitis, rapid neurological decline, and coma. In maple syrup urine disease, the brain concentration of branched-chain ketoacids can increase 10- to 20-fold. This leads to a depletion of glutamate and a consequent reduction in the concentration of brain glutamine, aspartate, alanine, and other amino acids. The result is a compromise of energy metabolism because of a failure of the malate-aspartate shuttle and a diminished rate of protein synthesis (PMID: 15930465).
Ketoleucine, also known as alpha-ketoisocaproic acid or 2-oxoisocaproate, belongs to short-chain keto acids and derivatives class of compounds. Those are keto acids with an alkyl chain the contains less than 6 carbon atoms. Ketoleucine is slightly soluble (in water) and a weakly acidic compound (based on its pKa). Ketoleucine can be found in a number of food items such as arctic blackberry, sesame, sea-buckthornberry, and soft-necked garlic, which makes ketoleucine a potential biomarker for the consumption of these food products. Ketoleucine can be found primarily in most biofluids, including saliva, blood, cerebrospinal fluid (CSF), and urine, as well as in human muscle, neuron and prostate tissues. Ketoleucine exists in all living species, ranging from bacteria to humans. In humans, ketoleucine is involved in the valine, leucine and isoleucine degradation. Ketoleucine is also involved in several metabolic disorders, some of which include methylmalonate semialdehyde dehydrogenase deficiency, propionic acidemia, 3-methylglutaconic aciduria type IV, and 3-methylglutaconic aciduria type I. Ketoleucine is a non-carcinogenic (not listed by IARC) potentially toxic compound. Ketoleucine is a metabolite that accumulates in Maple Syrup Urine Disease (MSUD) and shown to compromise brain energy metabolism by blocking the respiratory chain (T3DB).

4-Methyl-2-oxopentanoic acid (α-Ketoisocaproic acid), an abnormal metabolite, is both a neurotoxin and a metabotoxin.

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