Are the enzymes of interest metalloenzymes? Or require metal ions as cofactors? In general, ligand binding of halides to transition metals will follow I- > Br- > Cl- > F-. Halides, especially idodie, are known to inhibit certain zinc-metalloenzymes by displacing a catalytically active water molecule. In addition iodide may combine with and precipitate certain metal ions, and is also a weak reducing agent.
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Roger S. Rowlett
Gordon & Dorothy Kline Professor
Department of Chemistry
Colgate University
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On 8/5/2015 12:52 PM, rohit kumar wrote:

Dear All,

I am trying to check the affect of different halide on our enzyme. The reaction assay have 

 50 mM TAPS, pH 8.5, 0.2 mM NADH, 1.0 mM DTT, 1.0 mM EDTA,  5.0 mM substarte1, excess amount of PGDH, 5.0 mM substrate 2, and  4 µg of  enzymes (enzyme of interast). I am using 200 mM of halids (NaF, NaCl, NaBr and NaI) in separate reactions. 

In prsence of 200 mM NaF, NaCl, and NaBr the enzyme activity is not affected. But in case of NaI  > 50% activity is decreased. 

our enzyme does not have any halide binding site. 

Can any one just tell me why NaI give such affect? 

Is it because of bigger size of I (iodide ion)? or something else....

Please suggest 

 

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WITH REGARDS

Rohit Kumar Singh

Research Scholar