The role of active-site residues in naphthalene dioxygenase.

The three-component naphthalene dioxygenase enzyme system catalyzes the first step in the degradation of naphthalene by Pseudomonas sp. strain NCIB 9816-4. A member of a large family of bacterial Rieske non-heme iron oxygenases, naphthalene dioxygenase is known to oxidize over 60 different aromatic compounds, and many of the products are enantiomerically pure. The crystal structure of the oxygenase component revealed the enzyme to be an alpha(3)beta(3) hexamer and identified the amino acids located near the active site. Site-directed mutagenesis studies have identified the residues involved in electron transfer and those responsible for controlling the regioselectivity and enantioselectivity of the enzyme. The results of these studies suggest that naphthalene dioxygenase can be engineered to catalyze a new and extended range of useful reactions.