In: Chemistry
Which of the following located in the active site of the enzyme chymotrypsin participates in acid-base chemistry?
The side chain oxygen of serine
The amide group of glycine
The hydrophobic pocket Histidine
The amide group of serine
Answer :Histidine
Chymotrypsin cleaves the CO
of the amide bond.Chymotrypsin enzyme binding to its substrate
takes placein two number of steps:
1)Acyl-enzyme intermediate formation by substrate -acylation and then decylation to restore the enzyme.
2)Three amino acids catalyzes this reactions-histidine,aspartate
and Serine.Of these three the aspartate Oxygen binds to the N-delta
hydrogens of histidine (increasing the pKa of H on its e-H so that
it is activated to deprotonate serine. Serine on deprotonation
attacks the CO
of protein as nucleophile to cleave the CO-NH amide bond
Thus, histidine takes part in the acid -base rxn between the protein and the serine residue in the active site of chymotripsin.