Involved in the biosynthesis of the nonproteinogenic amino acid monomer (S)-3,5-dihydroxyphenylglycine (Dpg) responsible of the production of vancomycin and teicoplanin antibiotics. Catalyzes the unusual conversion 3,5-dihydroxyphenylacetyl-CoA (DPA-CoA) to 3,5-dihydroxyphenylglyoxylate. DpgC performed a net four-electron oxidation of the benzylic carbon of DPA-CoA and the hydrolysis of the thioester bond to generate free CoA. It can also use phenylacetyl-CoA (PA-CoA) as substrate. (3,5-dihydroxyphenyl)acetyl-CoA + O2 = 2-(3,5-dihydroxyphenyl)-2-oxoacetate + CoA + H(+) kcat is 10 min(-1) for dioxygenase activity. Homohexamer; dimer of trimers. Belongs to the enoyl-CoA hydratase/isomerase family.