A semiautomated kinetic assay of phenylalanine 4-hydroxylase

A semiautomated kinetic assay of phenylalanine 4-hydroxylase was developed and provided high sensitivity without radiochemical techniques. Dithiothreitol was used as a reductant to simplify the reaction mixture. The deproteination (dialysis) and tyrosine determination were carried out by an automated procedure using standard AutoAnalyzer equipment. The enzymatic activity in pCPA-treated and control rats was measured, and other possible applications of the procedure are discussed.