Nitrilotriacetate (NTA) is an aminotricarboxylic acid which generally binds bivalent metal ions in a ratio of 1:1. As an important industrial chelating agent, NTA has been widely used for various radionuclide processing and decontamination procedures, such as textile, paper and pulp processing and water treatment. The extensive use of NTA has led to considerable concern about the potential of NTA to resolubilize and mobilize heavy metals from sediments and activated sludge, which would result in a contamination of drinking water with metal-NTA complexes.
Fortunately, NTA is relatively easy to degrade. Many microorganisms, either in aerobic environments or under anaerobic or severely oxygen-limited conditions, can use NTA as sole source of carbon, nitrogen and energy. NTA biodegradation is initialized by nitrilotriacetate monooxygenase (aerobic) (Xu et al., 1997) or nitrilotriacetate dehydrogenase (anaerobic) (Jenal-Wanner and Egli, 1993), both of which hydroxylate NTA at an alpha-carbon atom and spontaneously form iminodiacetate (IDA) and glyoxylate. The nitrilotriacetate monooxygenase activity requires two component proteins, component A and B. Component A is an NTA monooxygenase which uses FMNH2 and O2 to oxidize NTA; component B is an NADH:FMN oxidoreductase that provides FMNH2 for NTA oxidization by using NADH to reduce FMN to FMNH2. In the follwing step, IDA is further converted to glycine and glyoxylate by iminodiacetate dehydrogenase.
The following is a text-format nitrilotriacetate acid pathway map. Organisms which can initiate the pathway are 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 (10k) format.
Nitrilotriacetate Nitrilotriacetate Chelatobacter heintzii ATCC 29600 Proteobacteria gamma subclass | | nitrilotriacetate | | nitrilotriacetate monooxygenase | | dehydrogenase | | | | +----------------+ +---------------+ | | v v Iminodiacetate + Glyoxylate | | iminodiacetate | | dehydrogenase | | | | | | v v Glycine + Glyoxylate---->Intermediary | Metabolism (KEGG) | | | | v Intermediary Metabolism (KEGG)
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