β-Leucine (beta-leucine) is a beta amino acid and positional isomer of -leucine which is naturally produced in humans via the metabolism of -leucine by the enzyme leucine 2,3-aminomutase. In cobalamin (vitamin B12) deficient individuals, plasma concentrations of β-leucine are elevated.
Biosynthesis and metabolism in humans A small fraction of metabolism – less than 5% in all tissues except the testes where it accounts for about 33% – is initially catalyzed by leucine aminomutase, producing β-leucine, which is subsequently metabolized into (β-KIC), β-ketoisocaproyl-CoA, and then acetyl-CoA by a series of uncharacterized enzymes.Figure 8.57: Metabolism of -leucine
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