One mechanism by which lead exerts its poisonous effect on enzymes can be stopped by chelation therapy with EDTA. Describe this type of lead poisoning and explain why it is reversible.

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All right. Hello everyone. So this question says that a reversible type of enzyme inhibition of mercury can be stopped by chelation therapy using DMSA describe this type of mercury inhibition. So before we go ahead and talk about the role of D MS A with mercury, let's just very quickly distinguish between the two types of enzyme inhibition inhibition. If you recall means that the activity of the enzyme is decreasing. So when it comes to reversible inhibition, reversible inhibition is the consequence of a metal like mercury displacing another metal that is an essential cofactor for the enzyme itself. Examples of cofactors, specifically metal cofactors are zinc, copper and iron. These are all metals that are very commonly found in our bodies. So essentially these metal cofactors were attached to the enzyme itself via a non covalent interaction. So when mercury does the same thing, it can detach itself from the enzyme at some point. This is in contrast to irreversible inhibition and irreversible or rather irreversible inhibition. It's characterized by the formation of a covalent bond and mercury in particular is unique in that it has a relatively high affinity for sulfur. It tends to gravitate towards other molecules that contain sulfur atoms. An example that's relevant in our bodies is the amino acid cysteine because cysteine specifically has these free file or S groups at the very end of their residues of the residue structure. So mercury gravitates towards these style groups and binds to them covalent and so a covalent bond to this cysteine residue is going to irreversibly inhibit the enzyme. Now, mercury is not alone in this because mercury is considered a heavy metal. So other heavy metals like cadmium, arsenic and lead can affect enzymes in the same ways that we described for mercury specifically. So when it comes to the role of DMSA in chelation therapy, it's worth remembering that when mercury is displacing these metal cofactors, mercury is going to participate in the same non covalent interaction that the co factors used to participate in. That's why the process is reversible because that interaction is not covalent. And so D MS A stands for dimercaptosuccinic acid. And it's a compound that contains sulfur specifically. But DMSA and other chelating agents are effective in that they form a complex with mercury. And so when they form a complex with mercury, mercury is going to to distance itself from the enzyme and it's going to leave the active site alone. So that a metal cofactor like zinc, copper or iron can go ahead and be reintroduced into the enzyme itself. And so with that, we've arrived at our final answer, which I've prewritten on the bottom of the screen here. The final answer reads as follows, the reversible type of mercury inhibition happens when it displaces an essential metal cofactor. And so with that being said, thank you so very much for watching. And I hope you found this helpful.

One mechanism by which lead exerts its poisonous effect on enzymes can be stopped by chelation therapy with EDTA. Describe this type of lead poisoning and explain why it is reversible.

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Key Concepts

Lead Poisoning

Chelation Therapy

Reversibility of Lead Poisoning