Studies on the formation of 3,4-dihydroxyphenylalanine, m-tyrosine and o-tyrosine from L-phenylalanine by rat liver and adrenal.

Abstract

Incubation of L-phenylalanine with the soluble fractions of liver and adrenal in the presence of a pterine cofactor, 2-mercaptoethanol and catalase gave rise to a hydroxylated compound which was identified as 3, 4-dihydroxyphenylalanine (DOPA), as well as p-, m- and o-tyrosines, on the basis of reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection. Chromatographic peaks were identified on the basis of their retention behavior and the assignment of the DOPA peak of HPLC was verified by ion-exchange chromatographic analysis.The formation of DOPA from L-phenylalanine by purified phenylalanine hydroxylase [EC 1.14.16.1] and tyrosine hydroxylase [EC 1.14.16.2] from rat liver and adrenal, respectively, was observed. The hydroxylation of L-phenylalanine to m- and o-tyrosines was also found to be catalyzed by the purified phenylalanine and tyrosine hydroxylases. In addition, the hydroxylation of L-p-tyrosine to DOPA was caused by the purified phenylalanine hydroxylase.