Carboxy Peptidase

 Carboxypeptidase refers to a group of enzymes that hydrolyze (break down) peptide bonds at the carboxyl-terminal (C-terminal) end of proteins and peptides, releasing amino acids. These enzymes play a crucial role in protein digestion, post-translational modification, and various physiological processes.

Types of Carboxypeptidases

Carboxypeptidases are broadly classified into two major categories based on their catalytic mechanism:

1. Metallo-Carboxypeptidases

• Require a metal ion (usually zinc, Zn²⁺) for catalytic activity.
• Found in digestive enzymes and regulatory proteins.
• Examples:
  • Carboxypeptidase A (CPA) – Cleaves hydrophobic (non-polar) amino acids.
  • Carboxypeptidase B (CPB) – Cleaves basic amino acids (arginine, lysine).
  • Carboxypeptidase E (CPE) – Involved in neuropeptide and hormone processing.

2. Serine or Cysteine Carboxypeptidases

• Use an active-site serine or cysteine residue instead of a metal ion.
• Found in lysosomes and involved in protein degradation.
• Examples:
  • Carboxypeptidase Y – Found in yeast, involved in protein processing.
  • Cathepsin A – Involved in lysosomal protein degradation.

Functions of Carboxypeptidases

• Protein digestion (e.g., pancreatic carboxypeptidases in the intestine).
• Regulation of bioactive peptides (e.g., neuropeptide processing).
• Wound healing and blood clotting (e.g., thrombin-activating carboxypeptidases).
• Post-translational modification (e.g., enzyme activation in the Golgi apparatus).

Medical and Biotechnological Importance

• Diagnostic markers for pancreatic and metabolic disorders.
• Therapeutic targets in diseases like hypertension and cancer.
• Enzyme inhibitors (e.g., carboxypeptidase inhibitors) are used in drug design.

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