Amino acid and organic acid metabolism disorders include Branched-chain amino acid disorders Methionine metabolism disorders Phenylketonuria Tyrosine metabolism disorders Ureacycle disorders In addition, there are a number of other disorders of amino acid and organic acid metabolism, including those involving beta - and gamma-amino acids, the gamma-glutamyl cycle, glycine, histidine, lysine, proline and hydroxyproline, and miscellaneous other amino acid disorders.