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Clarification of a prosthetic group
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cminors
#1 Posted : Saturday, June 04, 2011 9:26:28 PM
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Just need clarification on the exact definition of a prosthetic grp...
Exam crackers Bio book says it is a type of coenzyme, that binds irreversibly to an enzyme (p. 11-12) but the in-class companion says "a coenzyme or metal ion covalently bound to the enzyme is called a prosthetic group." So which is correct?

Thanks,
Chloe`
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mortezarazavi
#2 Posted : Sunday, June 05, 2011 2:26:46 AM
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Hi Chloe,
A prosthetic group is a cofactor (can be a coenzyme or metal ion) that is TIGHTLY bound to the enzyme. The stress is on tight interaction with the enzyme.

So in the EK page 12, 3rd line it says:" Prosthetic groups remain COVALENTLY bound to the enzyme THROUGHOUT the reaction and like the enzyme emerge from the reaction UNCHANGED". Therefore it is important to note that although they are tightly bound to the enzyme they are regenerated at the end of the reaction. Same thing can be inferred from the sentence in the CC: "A coenzyme or metal ion COVALENTLY bound to the enzyme" again the stress is on tight interaction during the reaction.

I hope this helps,

-Morteza
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matthewward
#3 Posted : Sunday, June 05, 2011 7:19:59 PM
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Chloe - as the author of the CC, I can certainly confirm with what Morteza has said - simply associate prosthetic group as something tightly bound (and therefore, often, but not always, covalently attached) to the enzyme. However, don't split hairs too much in your MCAT studying - just understand the basic idea here since an MCAT passage would discuss how the writer's want you to think about prosthetic groups on the real exam.

Thanks!
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