Question

Which of the following statements about the catalytic mechanism of serine proteases is TRUE?

	a.	The side chain of the catalytic triad aspartate residue directly engages in base catalysis to remove a proton from the side chain of the catalytic triad serine residue.
	b.	Cleavage of peptide bonds by a serine protease is likely to be insensitive to large changes in pH.
	c.	Mutation of the three catalytic triad residues to alanine would have no effect on the rate of catalysis.
	d.	The acyl-enzyme intermediate represents the transition state of the catalyzed reaction.
	e.	Catalysis by serine proteases incorporates steps in which the enzyme's amino acid side chains participate in breaking bonds in the substrate and in making and breaking bonds between the substrate and enzyme

Answer 1

•The correct statements about the catalytic mechanism of serine proteases are:

1.The side chain of the catalytic triad aspartate residue directly engages in base catalysis to remove a proton from the side chain of the catalytic triad serine residue.

2.The acyl-enzyme intermediate represents the transition state of the catalyzed reaction.

Hence, the correct options are (a and d).

Cleavage of peptide bonds by a serine protease is likely to be sensitive to large changes in pH.

Mutation of the three catalytic triad residues to alanine would have great effect on the rate of catalysis.

Hence, the options (b. c and e) are incorrect.