Chymotrypsin Mechanism - TBR

[anisidi1985]

So I'm going through Ch. 7 of TBR Biology (Book 2) and there is a subsection that discusses Enzyme mechanisms - it specifically goes into details about the chymotrypsin mechanism. Do we need to know this for the MCAT? I can't find the topic anywhere on the topic list from the AAMC.

Thanks in advance!

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[Shirafune]

I don't think you need to know the mechanism. But just some really quick takeaway facts about the mechanism and how it works:

1) Catalytic triad at its active site (serine, histidine, and aspartate)
2) Cleavage on carboxyl end of aromatic amino acids (tryptophan, phenylalanine, tyrosine)
3) Serine protease
4) Mechanism based on a nucleophilic serine that attacks the carbonyl in the peptide bond. Intermediates of the reaction come from proton transfer between Serine, Histidine, and the peptide bond.

 

[IslandStyle808]

It is one of those few I would suggest being familiar with. As to whether you need to memorize inside out, I am not sure since I have never seen a small intestine question on the MCAT. However, I would try to know them as well as possible.

 

[Czarcasm]

So I'm going through Ch. 7 of TBR Biology (Book 2) and there is a subsection that discusses Enzyme mechanisms - it specifically goes into details about the chymotrypsin mechanism. Do we need to know this for the MCAT? I can't find the topic anywhere on the topic list from the AAMC.

Thanks in advance!

I forgot the details, but from what I recall, it's no different than nucleophilic acyl substitution. Nucleophile attacks, Charged Tetrahedral Intermediate formation, LG leaves. In this instance though, everything occurs in sequence by very specific amino acids which all facilitate the process in someway. I think the 3 amino acids in the active site where serine, histidine, and aspartate ...aspartate (hidden inside the pocket) basically makes histidine a good proton acceptor, which allows serine (once it donates it's proton to his) to act as a good nucleophile ...this whole first part cleaves the N or C-terminus end (can't remember which), ...and the whole mechanism occurs again for the other peptide bond. Something like that. Honestly, only reason I remember this is because when I studied it for biochem, I realized it was no different than the orgo mechanism. It's not too bad, but it might help alleviate your concern if you watched a YT video on it. Might find it pretty interesting.

 

[sillyjoe]

So I'm going through Ch. 7 of TBR Biology (Book 2) and there is a subsection that discusses Enzyme mechanisms - it specifically goes into details about the chymotrypsin mechanism. Do we need to know this for the MCAT? I can't find the topic anywhere on the topic list from the AAMC.

Thanks in advance!

No way. Way over the top in that regard. If there is ANY question on it it will be addressed in the passage. TBR is probably just trying to get you to understand a concept of how enzymes work so if you ever came across a passage you wouldn't be befuddled.

 

[sillyjoe]

I don't think you need to know the mechanism. But just some really quick takeaway facts about the mechanism and how it works:

1) Catalytic triad at its active site (serine, histidine, and aspartate)
2) Cleavage on carboxyl end of aromatic amino acids (tryptophan, phenylalanine, tyrosine)
3) Serine protease
4) Mechanism based on a nucleophilic serine that attacks the carbonyl in the peptide bond. Intermediates of the reaction come from proton transfer between Serine, Histidine, and the peptide bond.

These facts are med school biochemistry facts. Good to know, but way more in depth than what you need to know for the MCAT.

 

[Shirafune]

These facts are med school biochemistry facts. Good to know, but way more in depth than what you need to know for the MCAT.

I agree, but knowing that it's a serine protease and what it cuts after isn't too much work if you have already taken biochem at your undergrad institution.

 

[anisidi1985]

Wow thank you all so much for your help! I'm pretty new to this website, and seeing all the immediate responses is really really great!