Evidence for the Involvement of Superoxide Anion in Dopamine-β-Hydroxylase System 1

Abstract

Summary

Dopamine-β-hydroxylase activity was markedly activated by a NADH-phenazine methosulfate-O₂ model system known to generate superoxide anion (O₂ ^-) in the absence of ascorbate. This activation of the enzyme activity was shown to be dependent on the concentration of phenazine methosulfate. When superoxide dismutase was added along with ascorbate to the system, DBH activity was markedly inhibited. Furthermore, the addition of the superoxide scavenger, nitro blue tetrazolium, to the enzyme either in the presence of ascorbate or NADH-phenazine methosulfate, resulted in the inhibition of DBH activity. These data suggest that O₂ ^- is essential for the enzyme activity and that the role of ascorbate is probable in the generation of O₂ ^-.