Tri-n-butyltin (TBT) is used as an antifouling agent in ship bottom paints. The pollution caused by TBT is widespread in coastal areas. At concentrations of 1 µg/L or less, TBT can be toxic to many marine organisms, including algae. Some types of microalgae can tolerate a TBT concentration of 25 µg/L and degrade TBT to dibutyltin (DBT), butyltin (MBT) and inorganic tin.
This pathway focuses on the microalgal biodegradation of TBT. The steps labeled as A, B, C are possibly catalyzed by enzyme action. beta-Hydroxylation is predominant during the degradation of TBT, however other types of hydroxylation are possible (Lee RF, Valkirs AO, Seligman PF Importance of Microalgae in the Biodegradation of Tributyltin in Estuarine Waters Environ Sci Technol 23: 1515-1518, 1989).
The following is a text-format tri-n-butyltin pathway map. Organisms which can initiate the pathway are given, but the 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 (12k) format.
Tri-n-butyltin (TBT) Diatoms bacillariophyta Dinoflagellates pyrrhophyta | | TBT dioxygenase | v beta-Hydroxybutyl- dibutyltin | | A | v to the Dibutyltin + Methyl ethyl ketone ------> MEK Pathway (DBT) (MEK) | | DBT dioxygenase | v beta-Hydroxybutyl- butyltin | | B | v to the Butyltin + Methyl ethyl ketone ------> MEK Pathway (MBT) (MEK) | | MBT dioxygenase | v alpha-Hydroxybutyltin | | C | v to the Tin + Methyl ethyl ketone ------> MEK Pathway (MEK)
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