The (2-alkyl)-3-hydroxy-4(1H)-quinolone-cleaving dioxygenase Hod has an α/β-hydrolase fold and a Ser/His/Asp triad in its active site. Isatoic anhydride, a suicide substrate of serine hydrolases, inactivates Hod by covalent modification of the active-site serine, thus indicating that the α/β-hydrolase fold can accommodate dioxygenase chemistry without completely abandoning hydrolase-like properties.