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Metabolite Card

CC[C@@H](C)[C@H](N)C(O)=O

Note

L-alloisoleucine is a branched chain amino acid and is a stereo-isomer of L-isoleucine. It is a common constituent of human plasma (albeit at low levels). L-alloisoleucine is produced as a byproduct of isoleucine transamination. L-Isoleucine is one of the four common amino acids (the 3 others being threonine, hydroxyproline, and hydroxylysine) that have two asymmetric carbon atoms which produce four structural possibilities for the same chemical composition. L-alloisoleucine differs from L-isoleucine by having having different stereochemistry around its beta carbon. Plasma L-alloisoleucine, which is derived from L-isoleucine in vivo, can be used for the diagnosis of maple syrup urine disease (MSUD), a genetic disorder. Indeed, plasma L-alloisoleucine levels above 5 umol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD (PMID: 10508118). In MSUD the degradation of the essential branched-chain L-amino acids leucine, valine, and isoleucine and their derived 2-oxoacids is impaired because of an inherited deficiency in branched-chain 2-oxoacid dehydrogenase complex (EC 1.2.4.4) activity. The accumulation of branched-chain compounds in blood and other body fluids can exert neurotoxic effects.