Extradiol ring fission dioxygenases

The second large group of ring-fission dioxygenases are used for the degradation of ortho-dihy-droxybenzoates including, 2,3-, 3,4-, and 4,5-dihydroxybenzoate. As for simple catechols, hssion may be either intradiol or extradiol, and the choice between them depends on the organism ... 

After formation of the 1,2-dihydroxy compounds, ring fission is mediated by 1 2 (intradiol fission) or 2 3 (extradiol and distal fission) dioxygenases. There are, however, important variations in the pathways used by various groups of microorganisms ... 

Attention has been drawn in Section 4.4.2 to the ability of naphthalene dioxygenase from Pseudomonas sp. strain 9816-4 to produce dibenzothiophene a s-l,2-dihydrodiol (Resnick and Gibson 1996). The transformation of naphtho[2,l-fr]thiophene and naphtho[2,3-fr]thiophene by Pseudomonas sp. strains grown with 1-methylnaphthalene has been examined (Knopp et al. 1997) as for the corresponding PAHs, the angular substrate (naphtho[2,l-b]thiophene) was more readily tranformed with the formation of hydroxybenzothiophene carboxylates by dioxygenation of the outer benzene ring followed by extradiol fission. 

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