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].