3. You have isolated a novel proteolytic enzyme and are analyzing the cleavage p

Question

3. You have isolated a novel proteolytic enzyme and are analyzing the cleavage properties of the purthed pro tein. You analyze the ability of the enzyme to catalyze cleavage of peptide bonds in small peptides. Your results are summarized in the table below (the "" indicates the peptide bond cleaved in each substrate). (2.5 points) Substrate KM (mM)Keat (s EMTA/G EMTA/A EMTA/ 4.0 1.5 0.5 24 30 18 If you presented a mixture of these peptides to the enzyme (in equimolar concentrations), which peptide would be digested most rapidly? Which would be digested most slowly? Explain your reasoning. (Hint: first determine the catalytic efficiency of the enzyme for each substrate).

Explanation / Answer

Ans. When determining the relative efficiency of the same enzyme towards different substrate, the term “catalytic efficiency” is preferred.

Catalytic efficiency = Kcat / Km

Greater is the value of catalytic efficiency for a substrate, the more efficient is the enzyme towards catalysis of that substrate.

#I. Catalytic efficiency for EMTA/G = 24 s-1 / 4.0 mM = 6.0 mM-1 s-1

#II. Catalytic efficiency for EMTA/A = 30 s-1 / 1.5 mM = 20.0 mM-1 s-1

#III. Catalytic efficiency for EMTA/F = 18 s-1 / 0.5 mM = 36.0 mM-1 s-1

Result: Peptide EMTA/F with highest catalytic efficiency will be digested most rapidly. Peptide EMTA/G with lowest catalytic efficiency will be digest most slowly.

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