EK Biology: prosthetic groups

[anbuitachi]

EK biology book says Prosthetic groups are organic (p11). Wiki says they may be organic and I heard that from various places as well. So is EK wrong? Can they be both organic and inorganic?

Thanks

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[JFK90787]

I think they can be either. The important thing to remember is that prosthetic groups are never proteins and they are closely associated with the active site (I.E covalently bound).

Also, an apoenzyme is an enzyme that doesn't have its associated cofactor present, and a holoenzyme is an enzyme that has its associated cofactor.

I learned a lot about enzyme definitions from EK, don't know if any of that terminology is on the actual test though since I haven't seen it in any of my practices

One thing I've always wondered any maybe someone here can answer, do cofactors have to be associated with an enzyme's active site? I know a cofactor is necessary for the proper function of an enzyme but that doesn't imply where it needs to be bound.

 

[DendWrite]

One thing I've always wondered any maybe someone here can answer, do cofactors have to be associated with an enzyme's active site? I know a cofactor is necessary for the proper function of an enzyme but that doesn't imply where it needs to be bound.

This is a good question. I don't know the right answer. Basically if a cofactor increases catalytic activity though, I'm assuming that it doesn't play a structural role (in bringing two subunits together for instance) a) because that one beneficial interaction would be unlikely to hold the two subunits together (there are probably tons of hydrogen bonds / etc between the two chains) and b) you can't "increase" activity if there is none to begin with.

I haven't personally heard of a case where a cofactor does not (at least peripherally) interact with the active site. So I'd guess that they are always close enough to be able to donate electrons / participate in redox rxns, etc. I definitely could be wrong, though, so if someone else knows, please post.