HIV protease shows similar substrate cleavage specificity to Chymotrypsin due to
ID: 985925 • Letter: H
Question
HIV protease shows similar substrate cleavage specificity to Chymotrypsin due to similar substrate binding pockets. Given the following sequence for the substrate peptide A written in the N-terminus to C-terminus direction, indicate the two amino acids between which the peptide bond will be cleaved t-l-a-r-d-y-k-g HIV protease has two aspartates in its active site. Even though both of the aspartates are mutated to alanines, the enzyme still retains higher enzymatic activity compared to the noncatalyzed reaction. How do you explain this observation? From the three amino acids in the peptide sequence D - T - G, which amino acid will you choose to make a buffer at pH 4.5? Why? Start with 0.05 M of the base form of your amino acid and calculate the concentration of the acidic form needed to have your buffer at the desired pH of 4.5. Use pKa values for this math problem from the table on last page of the exam. Show work with correct units.Explanation / Answer
(a) Chymotrypin splits peptide bonds in which the carbonyl group is part of phenylalanine, tyrosine or tryptophan.
Therefore in the given peptide chain Y is code for tyrosine and produce two fragments shown below
T-L-A-R-D-Y + K-G
(b) Carboxylate group of two aspartates in active site is involved in catalysis. Side chain of aspartate has no role in catalysis. Therefore its mutation to alanine does not affect the catalytic property of HIV protease.
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