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Leucine ball and stick model spinning. Leucine (symbol Leu or L) [3] is an essential amino acid that is used in the biosynthesis of proteins.Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH 3 + form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO − form under biological conditions), and a side ...
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Transamination is mediated by several types of aminotransferase enzymes. An aminotransferase may be specific for an individual amino acid, or it may be able to process any member of a group of similar ones, for example the branched-chain amino acids, which comprises valine, isoleucine, and leucine.
In humans, non-essential amino acids are synthesized from intermediates in major metabolic pathways such as the Citric Acid Cycle. [2] Essential amino acids must be consumed and are made in other organisms. The amino acids are joined by peptide bonds making a polypeptide chain.
Leucine is an essential amino acid, and its degradation is critical for many biological duties. [ 3 ] α-KIC is produced in one of the first steps of the pathway by branched-chain amino acid aminotransferase by transferring the amine on L-leucine onto alpha ketoglutarate , and replacing that amine with a ketone .
The Food and Nutrition Board (FNB) of the U.S. Institute of Medicine set Recommended Dietary Allowances (RDAs) for essential amino acids in 2002. For leucine, for adults 19 years and older, 42 mg/kg body weight/day; for isoleucine 19 mg/kg body weight/day; for valine 24 mg/kg body weight/day. [6]
Leucine, like valine, regulates the first step of its pathway by inhibiting the action of the α-Isopropylmalate synthase. [18] Because leucine is synthesized by a diversion from the valine synthetic pathway, the feedback inhibition of valine on its pathway also can inhibit the synthesis of leucine.
β-Leucine (beta-leucine) is a beta amino acid and positional isomer of L-leucine which is naturally produced in humans via the metabolism of L-leucine by the enzyme leucine 2,3-aminomutase. [ 1 ] [ 2 ] [ 3 ] In cobalamin (vitamin B 12 ) deficient individuals, plasma concentrations of β-leucine are elevated.