Isoleucine is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group, an α-carboxylic acid group, and a hydrocarbon side chain with a branch. It is classified as a non-polar, uncharged, branched-chain, aliphatic amino acid. Foods that have high amounts of isoleucine include eggs, soy protein, seaweed, turkey, chicken, lamb, cheese, and fish (see: Wikipedia).