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A very intesting question as a matter of fact. Generaly the answer is no they can't be removed from the active site becuase of the covalent bound. And yet we have some enzymes in our body we not always need like pepsin, trypsin and chymotrypsin. These enzymes are in a inactive state when not used and are called pepsinogen, trypsinogen and chymotrypsinogen and all belong to the group zymogen. A zymogen is an inactive enzyme precursor and requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme. This idea is very similar to the idea about irreversible inhibitation. So I would belive that if you had another enzyme that is able to catalyze the reaction that remove the irreversible inhibitor from the enzyme, then yes they could be removed. But why do we then generaly say they can't be removed? Well might just be becuase we haven't found any enzyme that can catalyze such a reaction - and if we have, we have might just given it another name, like zymogen.
I am also wondering are these enzyme would be broken down by cell or not?
Hmm think that depends on the situation, but my primary answer would be no. Like misfolded protein can't be brokken down, the enzyme can might just not be brokken down aswell. Another thing is that almost all nonreversible inhibitors are toxic substances, and are sometimes referred to as “suicide-inhibitors”. They got that additional name because the enzyme inactivates itself, because it reacts with the “false substrate” (inhibitor). An example of a nonreversible inhibitor is the nerve gas sarin. Sarin was used at the terrorist attack in Tokyo’s subways in 1995. Sarin is very poisonous, if 100 people in 1 min are exposed for a gas concentration on 100 mg/m3, about half would die. Sarin can bind to the enzyme acetylcholinesterase.
Hey, i just learn something from my lectures. Pralidoxime can be used to displace sarin or other organophosphate from the enzyme, provided it was given within few hours as the enzyme ages within few hours. Oh yes, isn't that misfolded protein undergoes ubiquination and then send to degradation?
Sounds true, but that is somehow connected to theory i have presented, pralidoxime binds to in the inhibited acetylcholinesterase causing serin to become unstable which results in the destruction of the covalent bond between sarin and acetylcholinesterase. See attachments for a molecular model of inhibition and regeneration.
"Oh yes, isn't that misfolded protein undergoes ubiquination and then send to degradation?" some misfolded proteins can't be brokken down that is what happens in mad cow disease - a accumulation of misfolded proteins