Cloning, sequence analysis, and expression of the Pseudomonas putida 33/1 1H-3-hydroxy-4-oxoquinoline 2,4-dioxygenase...

1H-3-hydroxy-4-oxoquinoline 2,4-dioxygenase (Qdo) from the 1H-4-oxoquinoline utilizing Pseudomonas putida strain 33/1, which catalyzes the cleavage of 1H-3-hydroxy-4-oxoquinoline to carbon monoxide and N-formylanthranilate, is devoid of any transition metal ion or other cofactor and thus represents a novel type of ring-cleavage dioxygenase. Gene qdo was cloned and sequenced. Its overexpression in Escherichia coli yielded recombinant His-tagged Qdo which was catalytically active. Qdo exhibited 36% and 16% amino acid identity to 1H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase (Hod) and atropinesterase (a serine hydrolase), respectively. Qdo as well as Hod possesses a SXSHG motif, resembling the motif GXSXG of the serine hydrolases which comprises the active-site nucleophile (X=arbitrary residue).