[Neuroscience] Horse Radish Peroxidase -DAB Reaction

[Bill]

Hi,

Does the chromogenic reaction of HRP with DAB actually require H2O2 at
the same time? That is to say, in an isolated system (with no
endogenous peroxisdases to complicate things), does HRP + DAB = BROWN
require H2O2? If so, how is that reaction actually happening, i.e.
what is being released or consumed by the HRP such that DAB reacts?

Thanks