Dopamine-β-hydroxylase: Stimulation by nitrogen-containing heterocyclics and the role of catalase.

The catalase inhibitor 3-amino-1,2,4-triazole causes an increase in dopamine-β-hydroxylase (DBH) activity, as do other nitrogen-containing heterocyclics. Denatured catalase also causes an increase in activity, but in both cases, optimum activity is attained only in the presence of some native catalase. It is proposed that the latter affects the DBH reaction in two different ways: It decomposes toxic peroxides, and it stabilizes the enzyme in some manner as yet unknown, as do the heterocyclics. The nitrogen-containing compounds, and denatured catalase, protect DBH from inhibition by copper. Ideas concerning the relationships of copper, catalase, and DBH must be altered to accommodate these new data.