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Catalytic Mechanism of Carboxypeptidase A

1) Carboxypeptidase A, a zinc-containing enzyme, hydrolyzes the C- terminal peptide bonds of polypeptides and/or proteins. In the enzyme- substrate complex, the zinc ion is coordinated to three enzyme side chains, the carbonyl oxygen of the scissile peptide bond, and a water molecule. A plausible model for the enzyme's reaction mechanism that is consistent with X-ray and enzymological data is diagrammed below.

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Solution Preview

Which of the following statements best describes the role of Glu270 in the catalytic mechanism of Carboxypeptidase A? Choose the single best answer.

a. Glu270 engages in covalent catalysis, forming a covalent linkage to the polypeptide substrate.
b. Glu270 causes strain & distortion of the polypeptide substrate, in much the same way that lysozyme distorts the substrate hexose ring into a half-chair conformation
c. Glu270 initially engages in acid catalysis, via extraction of a proton from the water molecule.
d. ...

Solution Summary

The solution discusses a plausible model for carboxypeptidase A.