Dioxygenases intradiol

Dioxygenase. Although it is not involved in the transformation of PAHs, it may be noted for the sake of completeness that a catechol intradiol dioxygenase is involved in the fission of 1,2,4-trihydroxybenzene that is formed from a number of aromatic substrates (Rieble et al. 1994). 

Because ferric iron does not react with triplet oxygen, intradiol dioxygenases must use a mechanism besides oxygen activation as the first step. 

Fig. 7. Model for oxygen activation by intradiol dioxygenases. PCA, the substrate pro-tochatechuic acid.

Intradiol dioxygenases prime their substrate for direct reaction with O2 by inducing radical character in the organic... 

Figure 3 Illustration of possible partial reaction cycles of some oxygenase enzymes. Water molecules and protein ligands have sometimes been omitted for clarity, (a) P450 (18) (b) intradiol dioxygenase (7) (c) lipoxygenase (7) (d) a-KG-dependent non-heme Iron enzymes (14) (e) soluble methane monooxygenase (15) (f) uncoupled blnuclear copper (16) (g) coupled blnuclear copper (h) flavin monooxygenases (17).

The intradiol dioxygenases catalyze the cleavage of catechols to cis, c/s-muconic acids4). 

The visible spectra of the intradiol dioxygenases (Fig. 2) are characterized by a broad absorption band centered near 460 nm with molar extinction coefficients of 3000-4000 M-1 cm-1 16>34). The color disappears upon reduction of the ferric ion with dithionite and is regenerated upon exposure of the solution to oxygen. Resonance Raman studies on these enzymes15 35-38) have been reported by several laboratories (Table 4). These spectra are characterized by a set of four peaks at ca. 1605, 1505, 1270, and 1175 cm-1, which are assigned to ring vibrations of Fe(III) coordinated tyrosinate ligands. Similar spectra are obtained for the transferrins as well as for model iron-phenolate complexes (Table 4). A new class of iron proteins seems to... 

In contrast to eukaryotes, bacteria such as Pseudomonas putida employ non-heme-containing dioxygenases in benzene metabolism [6-14. Harpel and Lipscomb [42] postulated that intradiol dioxygenases chelate the substrate (see 35) and the ring-opened product (see 36) releasing (Z,Z)-muconic acid (4a) (see Scheme... 

With one exception, in all the substrates the ene-diol structure is part of an aromatic nucleus. Oxidative cleavage of the ene-diol yields a dicarboxylic acid which retains the geometry of the remaining double bonds. There are eight of these so-called intradiol dioxygenases (/, 2, 83). 

Protocatechuate intradiol dioxygenase (E.C. 1.13.11.3 - Protocate-chuate oxygen 3,4-oxidoreductase (decyclizing)... 

Fujiwara, M., L. a. Golovleva, Y. Saeki, M. Nozaki, and O. Hayaishi Extradiol Cleavage of 3-Substituted Catechols by an Intradiol Dioxygenase, Pyrocatechase, from a Pseudomonad. J. Biol. Chem. 250, 4848 (1975). 

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