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Ronna Torres: The
effect of Tributyl Tin (TBT) on Glutathione-S-Transferase (GST)
on the common garden snail Helix
aspersa.
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Spectroscopic assays have been developed using the
specificity of GST for GSH to study the conjugation of CDNB substrate as
a measure of GST functionality.
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Depending upon the reaction conditions, the assay
permits not only the quantification of GST activity in samples, but also
provides a methodology for assaying GSH in complex cellular matrices (See
Figure 7).
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Based on this study, TBT inhibits GST activity.
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Results indicate that TBT is a noncompetitive inhibitor
of molluscan GST as shown by similar Km values and significant decrease
in Vmax.
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GST efficiency is substantially reduced by
the noncompetitive inhibition of TBT and this, together with the inhibitory
effect of TBT on Cytochrome-P450, may explain the build up of androgens
in molluscs.
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TBT and other endocrine disruptors that cause
imposex are of major concern because they can lead to extinction of marine
molluscs.
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Future studies should be carried out to quantify
the amount of GSH present in the cytosol. GSH plays an important role in
elimination process of toxic hydrophobic compounds in vivo. Also, less
harmful and equally effective antifouling agents should be developed to
replace TBT.
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