Debate and discussion of any biological questions not pertaining to a particular topic.

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Post by Dominf » Sun Apr 06, 2008 11:11 pm

Note: I'm really sorry this is in the wrong forum, I'm such a novice that even after reading all the descriptions I had no idea where this would go.

There are 2 parts to my question:

1. Are Lead Nitrate and Zinc Sulphate noncompetitive inhibitors?
2. Why is lead nitrate better at acting as an inhibitor? What generally makes some inhibitors better than others in certain situations? (From what I know I'm guessing there'd be different answers depending on whether they're competitive or noncompetitive, so please answer accordingly.)

Thank you :)

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Re: Inhibitors

Post by blcr11 » Tue Apr 08, 2008 3:20 pm

1) That kind of depends on the enzyme.
2) I don’t quite know how to answer the question.

Lead is generally more toxic than zinc because it binds readily to sulfurs and tends to disrupt or precipitate proteins. Zinc, on the other hand, ligates preferentially to histidines (His) and carboxylates (Asp or Glu), but only rarely to sulfur (Cys, and disulfide bridges)—there are notable exceptions, but when zinc binds to sulfur, it more often than not is binding to a critical Cys in the active site of an enzyme, not to just any old sulfur atom that happens to be lying around. If you consider disruption of protein structure to be a form of non-competetive inhibition, I suppose that lead is more disruptive than zinc, but it’s not really so much of a matter of kinetics as it is the status of the protein.

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