Part of the multicomponent 3-phenylpropionate dioxygenase. Converts 3-phenylpropionic acid (PP) and cinnamic acid (CI) into 3-phenylpropionate-dihydrodiol (PP-dihydrodiol) and cinnamic acid-dihydrodiol (CI-dihydrodiol), respectively. 3-phenylpropanoate + H(+) + NADH + O2 = 3-(cis-5,6-dihydroxycyclohexa-1,3-dien-1-yl)propanoate + NAD(+) (E)-cinnamate + H(+) + NADH + O2 = (2E)-3-(cis-5,6-dihydroxycyclohexa-1,3-dien-1-yl)prop-2-enoate + NAD(+) Aromatic compound metabolism; 3-phenylpropanoate degradation. This dioxygenase system consists of four proteins: the two subunits of the hydroxylase component (HcaE and HcaF), a ferredoxin (HcaC) and a ferredoxin reductase (HcaD). Belongs to the bacterial ring-hydroxylating dioxygenase beta subunit family.