Intradiol catechol dioxygenase

Dioxygenase enzymes are known that contain heme iron, nonheme iron, copper, or manganese.The substrates whose oxygenations are catalyzed by these enzymes are very diverse, as are the metal-binding sites so probably several, possibly unrelated, mechanisms operate in these different systems. For many of these enzymes, there is not yet much detailed mechanistic information. However, some of the intradiol catechol dioxygenases isolated from bacterial sources have been studied in great detail, and both structural and mechanistic information is available. These are the systems that will be described here. 

Unlike the intradiol catechol dioxygenases, the extradiol catechol dioxygenases retain all of their endogenous ligands throughout the catalytic cycle. It is suggested that substrate binding to the... 

Table 1. Comparison of relative catalytic activities of oxygenation of substituted catechols by intradiol catechol dioxygenases ... 

Importance of the ferrous state for dioxygenation is mostly observed, but intradiol catechol dioxygenases and lipoxygenase require the ferric state for oxygenation. The oxidation state of iron important for oxygenation is sometimes different from that of isolated enzymes and in the resting state. In the enzymes which require the ferric state, activation of substrate by the iron center seems to proceed in preference to that of oxygen, and vice versa in the ferrous enzymes. 

Orville AM, Lipscomb JD. 1997. Cyanide and nitric oxide binding to reduced proto-catechuate 3,4-dioxygenase insight into the basis for order-dependent hgand binding by intradiol catecholic dioxygenases. Biochemistry 36(46) 14044—14055. 

Bugg, T. D. H., and Lin, G., Solving the Riddle of the Intradiol and Extradiol Catechol Dioxygenases How Do Enzymes Control Hydroperoxide Rearrangements. J. Chem.Soc. Chem. Commun., 2001. pp. 941-952. 

Figure 15 Proposed substrate activation mechanism for the intradiol cleaving catechol dioxygenases.

Figure 6 Proposed substrate activation mechanism for intradiol-cleaving catechol dioxygenases. Substrate activation is proposed to occur via an iron(II)-semiqumone prior to O2 binding...

The intradiol cleaving catechol dioxygenases are bacterial iron-containing enzymes that serve as a component of nature s mechanism for degrading aromatic compounds in the environment. These enzymes, represented by catechol 1,2-dioxygenase (CTD) and protocatechuate(3,4-dihydroxybenzoate) 3,4-dioxygenase (PCD), catalyze the reaction... 

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