cofactors and coenzymes, prosthetic groups

[andyjl]

i've read and keep hearing different things about these..like cofactors and coenzymes are the same, or cofactors are mostly vitamins, another source says vitamins are mostly prosthetic groups.

can someone clear this up?

can someone give definitions of each and examples of each of those?

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[laundry]

I would say that the best way to classify enzymes is thusly (if that's a word):

Enzymes are proteins. Co-factors are mostly Ions (Mg2+, Fe2+), which bind to the enzyme. Those ions are classified as prosthetic groups and they contribute to the quaternary structure of the protein. Vitamins are also co-factors bound as prostheric (non-amino) groups. Co-enzyme is a broader term, including co-factors. However, a co-enzyme can be non-vitamin and non-metal (thus not a co-factor), such as FAD or CoA.

Co-factor enzymes include your basic hemoglobin, P680 and P720 of the chloroplasts.

hope this makes sense (or is accurate )

 

[Dotoday]

Hi guys, a little correction here. Not all enzymes are proteins. There are RNA molecules that can now act as enzymes. So broadly speaking, enzymes are catalysts, they catalyse the reaction by lowering activation energy. They shift equilibrium to the right. Now as for the cofactors, yes they are mostly ions. Cofactors are necessary molecules for the enzymes. For example, DNA polymeraze needs MgCl2 in order to function.
Prosthetic groups, are basically nonpeptide molecules that are found in proteins. Yes for example Hemoglobin and Myoglobin have Protoporphyrin rings that are prosthetic groups that are also needed for the proteins to function. But overall they are the same, it is just smaller molecules like Mg, Cl, Copper are called cofactors, whereas larger size molecules like Protoporphyrin rings are called prosthetic groups. Yet their functions are the same.
I hope that answers your question. Good luck studying.

 

[Bob Faraples]

They shift equilibrium to the right.

It is my understanding that an enzyme (catalyst) should not alter the equilibrium to the right or the left - instead they allow the natural equilibrium to be achieved more quickly.

Wikipedia (word search: enzymes) agrees with me on this.

Correct me, please, with a reference so that we can inform Wikipedia if we are both wrong.