Assay of L-tyrosine in serum by amperometric measurement of tyrosinase-catalyzed oxygen consumption.

A new enzymatic method for rapid direct measurement of serum tyrosine is described, based on the amperometric measurement of the rate of oxygen consumption when tyrosine is oxidized in the presence of the enzyme tyrosinase in a phosphate buffer (0.1 mol/liter, pH 7.4). A Beckman Glucose Analyzer with a Clark electrode is used for the measurement. The procedure does not require removal of serum protein, incubation nor extraction, and results are obtained in less than 1 min. Results agree closely with those obtained by a fluorometric procedure and with an amino acid analyzer.