Classification of Protease

Protease, also known as peptidases or proteinases, are enzymes that catalyze the hydrolysis of peptide bonds in proteins. They play crucial roles in various biological processes, including digestion, cell signaling, and protein recycling. Protease is classified based on different criteria, such as their catalytic mechanism, active site residue, and specificity. Below is a detailed classification:

1. Based on Catalytic Mechanism

Protease is categorized by the nature of the active site group involved in catalysis:

（a）Serine Protease

    • Use a serine residue in their active site.
    • Examples: Trypsin, chymotrypsin, elastase.

    （b）Cysteine Protease

      • Use a cysteine residue in their active site.
      • Examples: Papain, caspases, cathepsins.

      （c）Aspartic Protease

        • Use aspartic acid residues in their active site.
        • Examples: Pepsin, renin, HIV protease.

        （d）Metalloprotease

          • Require a metal ion (often Zn²⁺) for activity.
          • Examples: Matrix metalloproteinases (MMPs), thermolysin.
          Classification of Protease-Xi'an Lyphar Biotech Co., Ltd

          (e) Threonine Protease

          • Use the hydroxyl group of a threonine residue for catalysis.
          • Examples: Proteasomes.

          (f) Glutamic Protease

          • Utilize a glutamate residue in their active site.
          • Example: Scytalidopepsin.

          2. Based on Site of Action

          This classification is based on the substrate specificity and where the protease acts:

          (a) Exopeptidases

          Act on the terminal ends of peptides.

          • Aminopeptidases: Remove amino acids from the N-terminal.
          • Carboxypeptidases: Remove amino acids from the C-terminal.

          (b) Endopeptidases

          Act within the peptide chain by cleaving internal peptide bonds.

          Examples: Trypsin, pepsin.

          3. Based on pH Optimum

          Protease is classified based on the pH at which they are most active:

          (a) Acidic Protease

          • Active in acidic pH.
          • Example: Pepsin.

          (b) Neutral Protease

          • Active in neutral pH.
          • Example: Trypsin.

          (c) Alkaline Protease

          • Active in basic pH.
          • Example: Subtilisin.

          4. Based on Structural Features

          Protease is also grouped based on their structural motifs or families:

          • Chymotrypsin-like serine proteases.
          • Papain-like cysteine proteases.
          • Aspartic protease family.
          • Metalloprotease family.
          Classification of Protease-Xi'an Lyphar Biotech Co., Ltd

          5. Functional Classification

          Protease may also be grouped based on their biological roles:

          • Digestive protease: Assist in breaking down dietary proteins (e.g., pepsin, trypsin).
          • Regulatory protease: Involved in cellular regulation (e.g., caspases in apoptosis).
          • Viral protease: Critical for viral replication (e.g., HIV protease).
          • Proteolytic processing enzymes: Help activate precursor proteins (e.g., prohormone convertases).

          This classification provides a comprehensive framework for understanding the diverse roles and mechanisms of protease in biological systems.