ABSTRACT
Nature employs the catechol dioxygenases as an element of her strat egy for degrading aromatic molecules in soil [1-3]. These enzymes cat alyze the oxidative cleavage of dihydroxybenzene rings with the incor poration of both atoms of dioxygen into the aliphatic products. Two families of catechol dioxygenases have been identified based on the po sition of ring cleavage (Fig. 1): intradiol, where the carbon-carbon bond of the enediol unit is cleaved, and extradiol, where the carbon-carbon bond adjacent to the enediol moiety is cleaved. Although they share many substrates, the intra-and extradiol-cleaving enzymes exhibit near-exclusivity in the regiospecificity of oxidative cleavage, indicating the existence of two distinctly different catalytic mechanisms [2,3]. Fur thermore, the intradiol-cleaving enzymes invariably require Fe(III), while the extradiol-cleaving enzymes usually require Fe(II). However, there are examples of extradiol-cleaving enzymes that require Mn(II) [4-6] and one that requires Mg(II) [7].