17.The enzyme elastase cleaves peptide bonds. The following data were obtained f

Question

17.The enzyme elastase cleaves peptide bonds. The following data were obtained for the cleavage of the following short peptides by elastase. (The * indicates the bond that is cleaved.) Substrate PAPG A PAPA*G PAPA A PAPA*F 9.0 4.0 1.5 0.64 kcat (s-1) 0.5 26 37 18 a. Which of these substrates would be preferentially cleaved by elastase Which would be cleaved most slowly? How do you know? (2) b. Based on this experimental evidence, which features of the peptide sequence determine the specificity of peptide cleavage by elastase? (2)

Explanation / Answer

17.
a. Among the substrates, PAPA*F would be preferentially cleaved by elastase since it has the lowest kM value among the other substrate.
PAPG*A would be cleaved most slowly. It has the highest kM value and lowest kcat value.

b. Elastase is a serine protease and cleaves the polypeptide chain at the ala-ala and ala-gly sequence.

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