The following kinetic parameters were measured for a proteolytic Enzyme X. The a
ID: 905482 • Letter: T
Question
The following kinetic parameters were measured for a proteolytic Enzyme X. The arrow indicates the cleavage site in each case. Remember the single letter amino acids.
Substrate
Km (mM)
Kcat (s-1)
EMTAG
4.0
24
EMTAA
1.5
30
EMTAF
0.5
18
EMTLF
9
18
a.) If an equimolar mixture of these peptides was presented to the enzyme, which peptide would be digested most effectively? Least effectively? Explain your reasoning, if any.
b.) If the above experiment was performed on another peptide and the following results were obtained:
Substrate
Km (mM)
Kcat (s-1)
EMTLF
9
18
On the basis of these data, suggest the features of the amino acid sequence that dictate the specificity of the enzyme.
Substrate
Km (mM)
Kcat (s-1)
EMTAG
4.0
24
EMTAA
1.5
30
EMTAF
0.5
18
EMTLF
9
18
Explanation / Answer
Answer: a)
EMTAG is more reactive, while EMTAF is least reactive.
Answer b)
Detailed analyses of protein structures provide an opportunity to understand conformation and function in terms of amino acid sequence and composition. In this work, we have systematically analyzed the characteristic features of the amino acid residues found in alpha-helical coiled-coils and, in so doing, have developed indices for their properties, conformational parameters, surrounding hydrophobicity and flexibility.
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