Chymotrypsin Mechanism: Correct Steps for Enzymatic Catalysis

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In summary, the correct steps for the mechanism of chymotrypsin are: Ser195's nucleophilic O attacks carbonyl C of substrate, followed by His57 catalyzing removal of H from Ser195 hydroxyl. Then, His57 donates H to N of sissile peptide bond, leading to decomposition of the tetrahedral intermediate. The C-terminal portion of the original substrate diffuses away with its new amino acid terminus. Water donates H to His57, and the resulting OH attacks the carbonyl of the remaining substrate. His57 then donates H to Ser195 O, causing the tetrahedral intermediate to collapse. Finally, the N-terminal portion of the original substrate diffuses
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what are the correct steps for the mechanism of chymotrypsin?

Below is my answer but I don't know if it is right.


a) His 57 catalyzes removal of H from Ser 195 hydroxyl.
b. Ser 195's nucleophilic O attacks carbonyl C of substrate.
c. His 57 donates H to N of sissile peptide bond, tetrahedral intermediate decomposes.
d. C- terminal portion of oribinal substrate with its new amino acid terminus diffuses away.
e. water donates H to His 57.
f. Resulting OH attacks carbonyl of remaining substrate.
g. His 57 donates H to Ser 195 O, leading to collapse of tetrahedral intermediate.
h.N-terminal portion of original substrate with its new carboxy terminus diffuses away.

My answer is b,a,c,e,f,g,h,d. Is this right? Thank you! :)
 
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Two comments/questions:

Why do you believe that the O of Ser195 would be nucleophilic before its proton was partially abstracted by His57?

Why do you believe that the substrate would remain in the reaction center if it is no longer involved in the reaction after step c?
 

FAQ: Chymotrypsin Mechanism: Correct Steps for Enzymatic Catalysis

What is the role of chymotrypsin in the digestive system?

Chymotrypsin is a digestive enzyme that helps break down proteins in the small intestine. It is produced by the pancreas and is essential for the digestion and absorption of dietary proteins.

What is the structure of chymotrypsin?

Chymotrypsin is a globular protein with a complex tertiary structure. It consists of three polypeptide chains held together by disulfide bonds. The active site of chymotrypsin is located in a deep pocket on the surface of the enzyme.

How does chymotrypsin catalyze the hydrolysis of proteins?

Chymotrypsin uses a process called covalent catalysis to break down proteins. The enzyme first binds to the protein substrate, bringing it close to its active site. Then, the active site undergoes a conformational change, allowing a serine residue to attack the peptide bond and break it apart.

What factors affect the activity of chymotrypsin?

The activity of chymotrypsin can be influenced by several factors, including pH, temperature, and the concentration of substrate and enzyme. Chymotrypsin has an optimal pH of 8 and works best at a temperature of 37°C, which is the body's normal temperature.

How is chymotrypsin regulated in the body?

Chymotrypsin is regulated by the body through feedback inhibition. When the concentration of chymotrypsin reaches a certain level, it signals the pancreas to stop producing more enzymes. Additionally, chymotrypsin is also regulated by other hormones and enzymes in the digestive system.

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