Dopamine formation from phenylalanine: independent existence in caudate nucleus synaptosomes

Dopa and dopamine formations from phenylalanine and tyrosine in rat caudate nucleus synaptosomal preparation were studied. Phenylalanine and tyrosine, labelled with either 14C or 3H, were employed as cosubstrates leading to the formations of double labelled Dopa and dopamine. The ratio of the two isotopes in dopamine was found to be significantly different from that in Dopa. The results suggest that Dopa formed from the cosubstrates are compartmented.