We investigated the time dependence of the degradation of three alkyltin derivatives by a nine amino acid linear peptide (I1LGCWCYLR 9) containing a CXC motif derived from the primary sequence of stannin, a membrane protein involved in alkyltin toxicity. We monitored the reaction kinetics using the intrinsic fluorescence of the tryptophan residue in position 5 of the peptide and found that all of the alkyltins analyzed are progressively degraded to dialkyl derivatives, following a pseudoenzymatic reaction mechanism. The end point of the reactions is the formation of a covalent complex between the disubstituted alkyltin and the peptide cysteines. These data agree with the speciation profiles proposed for polysubstituted alkyltins in the environment and reveal a possible biotic degradation pathway for these toxic compounds.
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Acknowledgments Acknowledgment is made to the donors to the Petroleum Research Fund, administrated by the American Chemical Society, for partial support of this research. B.B. was supported by NIH Chemical Biology Interface Training Grant GM-08700.
- Fluorescence spectroscopy
- Kinetics of dealkylation
- Organotin compounds