Dopamine-β-hydroxylase: Evidence for binuclear copper sites

Abstract Copper has been progressively removed from dopamine-β-hydroxylase by incubation with chelex resin. The relationship between the activity (A) and the copper/protein ratio (r) has been shown to be of the form A ⊥ r 2 which implies that the enzyme catalysed reaction is second order with respect to protein bound copper. These results support a model for the catalytic mechanism involving binuclear copper sites rather than the four copper atoms in the enzyme acting independently.