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6 carboxypeptidase mechanism

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advanced enzymology

Publié dans : Formation
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6 carboxypeptidase mechanism

  1. 1. Carboxypeptidase Mechanism
  2. 2. • Carboxypeptidase A is a digestive enzyme that hydrlyzes the carboxyterminal peptide bond in polypeptide chain.
  3. 3. Two aspects of catalytic mechanism will be discussed for carboxypeptidase A: • Induced Fit: The binding of substrate is accompanied by quite large alteration in the structure of the active site.
  4. 4. • Electronic strain: The enzyme contains Zinc atom and other groups at the active site that induce electronic rearrangement of the substrate to be more susceptible to hydrolysis.
  5. 5. • Carboxypeptidase A is a single polypeptide of 307 amino acid residues. • There is a tightly bound zinc ion which is essential for enzymatic activity.
  6. 6. • Zinc is located in a groove near the surface of the molecule ccordinated in a tetrahedral array of two histidine side chain, a glutamate side chain and a water molecule.
  7. 7. • The Carboxyl oxygen of the peptide bond to be cleaved is ccordinated with the zinc ion
  8. 8. 1-The tyrosine side chain of the substrate binds to the non-polar pocket in the active site of the enzyme. 2-The NH- hydrogen of the peptide bond to be cleaved is hydrogen bonded to the OH group of tyrosine 248. 3-The negatively charged terminal carboxylic group of glycyltyrosine (substrate) interacts electrostatically with the positively charged side chain of arginine 145
  9. 9. 4-The carboxyl oxygen of the peptide bond to be cleaved is coordinated to the zinc ion. 5-The terminal amino group of the peptide chain is hydrogen bonded through the water molecule to the side chain of glutamate 270.
  10. 10. Mechanism