Metabolism of an amino acid with antidepressant properties.

The amino acid D-phenylalanine exerts antidepressant properties which are believed to be due to its metabolism to brain phenylethylamine. We now show that in mice, the increase in brain phenylethylamine levels induced by L-phenylalanine, but not D-phenylalanine, is antagonized by drugs which block the stereospecific decarboxylase enzyme. Our results show that D-phenylalanine metabolism to phenylethylamine is independent of pathways involving L-phenylalanine.