Gallate is used in photographic ink, dyeing, paper manufacture, and engraving and lithography. The toxicological properties of gallate have not been fully investigated. It may cause eye, skin, respiratory and digestive tract irritation.
Polyphenolic compounds such as gallate, pyrogallol, and 1,2,4-trihydroxybenzene are stabilized by resonance and meta-substituted hydroxyl groups. Natural sources of theses compounds include plant flavonoids, tannins and lignin. Biodegradation occurs by aerobic pathways and anaerobic pathways in the absence of terminal electron acceptors.
The initial step in the anaerobic gallate pathway used by Eubacterium oxidoreducens G41 is the decarboxylation of the ring (Krumholz et al., 1987). Acetate, butyrate and carbon dioxide are end products of gallate fermentation. Oxidation of formate or hydrogen is required for growth on gallate to provide electrons for reduction of the ring prior to ring cleavage (Haddock and Ferry, 1989). Pelobacter acidigallici degrades gallate anaerobically, but produces only acetate (Brune et al., 1990). The reaction that transforms 3-hydroxy-5-oxohexanoate to 3-hydroxy-5-oxohexanoyl-CoA is proposed and still not well understood. This page shows only anaerobic pathway of gallate. The aerobic degradation of gallate is documented elsewhere in EAWAG-BBD.
The following is a text-format gallate anaerobic degradation 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 (13k) format.
Gallate (3,4,5-Trihydroxybenzoate) Eubacterium oxidoreducens G41 | | | gallate decarboxylase | | v Pyrogallol | | | pyrogallol transhydroxylase | | v Phloroglucinol | | | phloroglucinol reductase | | v Dihydrophloroglucinol | | | dihydrophloroglucinol hydrolase | | v 3-Hydroxy-5-oxohexanoate | | | [CoA transferase] | | v 3-Hydroxy-5-oxohexanoyl-CoA | | | 3-hydroxy-5-oxohexanoyl-CoA thiolase | | v Acetyl-CoA + (3S)-3-Hydroxybutyryl-CoA | | | | | | enoyl-CoA | | hydratase | | v v Intermediary Crotonoyl-CoA Metabolism | (KEGG) | | butyryl-CoA dehydrogenase | | v Butyryl-CoA | | | CoA transferase | | v Butyrate | | | | | v Intermediary Metabolism (KEGG)
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