Hydroxybenzoates and Related Compounds

Phenols and hydroxybenzoates are generally degraded by monooxygenation. Illustrative examples include the following  

The degradation of salicylate to catechol is initiated by monooxygenation accompanied by decarboxylation (salicylate-l-hydroxylase), and two different and independent salicylate hydroxylases have been found in the naphthalene-degrading Pseudomonas stutzeri ANIO (Bosch et al. 1999). Alternatively, in Rhodococcus sp. strain B4, salicylate is hydroxylated to 2,5-dihydroxybenzoate by salicylate-5-hydroxylase (Grand et al. 1992). An alternative occurs for 5-hydroxy- and 5-aminosalicylate in Pseudaminobacter salicylatoxidans in which ring fission is accomplished directly (Hintner et al. 2001). 

The monooxygenase from Pseudomonasfluorescens that converts 4-hydroxybenzoate into 3,4-dihydroxybenzoate before ring hssion has been characterized (Howell et al. 1972). 

In Pseudomonas putida, the hydroxylation of 4-hydroxyphenylacetate to 3,4-dihydroxy-phenylacetate is carried out by an enzyme that consists of a flavoprotein and a coupling factor (Arunachalam et al. 1992). At least in Escherichia coli, it has been suggested that the large component is an FADH2-utilizing monooxygenase (Xun and Sandvik 2000 Chaiyen et al. 2001). 

The hrst enzyme in the degradation of 2-hydroxybiphenyl by Pseudomonas azelaica strain HBPl is an FAD-dependent monooxygenase that produces 2,3-dihydroxybiphenyl (Suske et al. 1999). 

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Unusual pathways have been found in the bacterial degradation of a number of 4-hydroxybenzoates and related compounds, and in some of them rearrangements (NIH shifts) are involved ... 

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