In enzymology, a deacetoxycephalosporin-C synthase () is an enzyme that catalyzes the chemical reaction
<div align=center><small>penicillin N + 2-oxoglutarate + O<sub>2</sub> deacetoxycephalosporin C + succinate + CO<sub>2</sub> + H<sub>2</sub>O</small></div>
The 3 substrates of this enzyme are penicillin N, 2-oxoglutarate, and O<sub>2</sub>, whereas its 4 products are deacetoxycephalosporin C, succinate, CO<sub>2</sub>, and H<sub>2</sub>O.
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with 2-oxoglutarate as one donor, and the other dehydrogenated.
The systematic name of this enzyme class is penicillin-N,2-oxoglutarate:oxygen oxidoreductase (ring-expanding). Other names in common use include DAOCS, penicillin N expandase, and DAOC synthase.
This enzyme is involved in the biosynthesis of cephalosporin C in Acremonium chrysogenum, which is used for the industrial production of that antibiotic.
As of late 2007, 7 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , and .