Abstract
We describe a fully automated enzymatic method for the direct measurement of tyrosine and the three branched-chain amino acids (BCAA)-leucine, isoleucine, and valine-in plasma. For the tyrosine assay, we employed tyrosine decarboxylase, tyramine oxidase, and peroxidase; and for the BCAA assay, leucine dehydrogenase. We measured aromatic amino acids and BCAA in plasma from patients with hepatic disorders by this method and by use of an amino acid analyzer (AA). The results obtained by the two procedures correlated well (tyrosine, r=0.957; BCAA, r=0.970). The BCAA/tyrosine ratio by the method was shown to be as good as Fischer's ratio as an indicator for the diagnosis of liver diseases.
