Phenylacetate-CoA oxygenase/reductase, PaaK subunit Phenylacetate-CoA oxygenase is comprised of a five gene complex responsible for the hydroxylation of phenylacetate-CoA (PA-CoA) as the second catabolic step in phenylacetic acid (PA) degradation [<cite idref="PUB00005820"/>, <cite idref="PUB00010200"/>]. Although the exact function of this enzyme has not been determined, it has been shown to be required for phenylacetic acid degradation and has been proposed to function in a multicomponent oxygenase acting on phenylacetate-CoA [<cite idref="PUB00010200"/>].