The Phenol Family pathway map includes the aerobic metabolic pathways for phenol, phenolboronic acid, and diphenyl ether. Phenylboronic acid is an aromatic boronic acid. Boronic acids are used for a variety of purposes, including insect pest control (Settepani et al., 1970). Plant cell walls and some bacterial quorum-sensing molecules contain borate esters (O'Neill et al., 2001, Chen et al., 2002), and antibiotic compounds containing boron are synthesized by some bacteria (Irschik et al., 1995, Kohno et al., 1996).
The initial step in the degradation of phenylboronic acid can be carried out by Arthrobacter nicotinovorans strain PBA, which converts the compound to phenol under aerobic conditions (Negrete-Raymond et al., 2003). Boron is predicted to be released from phenylboronic acid as orthoboric acid (B(OH)3), although the production of this compound has not yet been experimentally verified. A. nicotinovorans strain PBA has also been shown to oxidize other aromatic boronic acids.
The yeast Trichosporon cutaneum (Gerginova et al., 2007) or the bacterium Brevibacterium fuscum (Nakagawa & Takeda, 1962), and several other bacteria, can aerobically degrade phenol to catechol. The anaerobic biodegradation of phenol is covered elsewhere.
Diphenyl ether (DE) and its halogenated cogeners are compounds of environmental concern. Polybrominated DEs (PBDEs) are used as flame retardants. Sphingomonas sp. strain SS3 aerobically degrades diphenyl ether and its monochlorinated derivatives through angular dioxygenation to phenol and catechol via cis-1,2-dihydrodihydroxydiphenyl ether (Schmidt et al., 1992). Sphingomonas strain PH-07 aerobically degrades diphenyl ether and its mono-, di-, and tri-brominated derivatives to 2,3-dihydroxydiphenyl ether, which it degrades to phenol and 2-hydroxymuconate (Kim et al., 2007).
The following is a text-format phenol family pathway map. An organism which can initiate the pathway is given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions. This map is also available in graphic(5k) format.
Diphenyl ether Sphingomonas sp. PH-07 | | diphenyl ether | 2,3-dioxygenase | v Phenylboronic acid 2,3-Dihydroxydiphenyl ether Arthrobacter nicotinovorans PBA | from the | | Permethrin Pathway | phenylboronic acid | 2,3-dihydroxydiphenyl \ | monooxygenase | ether dioxygenase \ | | \ v v Diphenyl ether ----------+--------> Phenol + 2-Hydroxymuconate Sphingomonas sp. SS3 | Brevibacterium fuscum | | Trichosporon cutaneum | | and others | | | | diphenyl ether | | phenol | 1,2-dioxygenase | | 2-monooxygenase | | | | | v v +--------> Catechol Intermediary | Metabolism | (KEGG) | | v to the Nitrobenzene Pathway
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