Proteases, also known as peptidases or proteinases, are enzymes that break down proteins by cleaving the peptide bonds between amino acids. They play essential roles in digestion, cell signaling, immune defense, development, and protein recycling.
🔑 Definition:
Proteases are enzymes that catalyze the hydrolysis of peptide bonds in proteins, converting them into smaller peptides or amino acids.
⚙️ How Proteases Work:
Proteases break proteins apart using water (hydrolysis). Each protease has a specific shape and often targets specific sequences or structures in proteins.
🔬 Types of Proteases (Based on Their Active Site Mechanism):
| Type | Key Feature | Example(s) |
|---|---|---|
| Serine proteases | Use a serine residue to cut bonds | Trypsin, chymotrypsin |
| Cysteine proteases | Use a cysteine residue | Caspases, papain |
| Aspartic proteases | Use aspartic acid residues | Pepsin, renin |
| Metalloproteases | Require a metal ion (usually zinc) | Matrix metalloproteinases (MMPs) |
| Threonine proteases | Use threonine (e.g., in proteasome) | Proteasome catalytic core |
🍽️ Examples in the Human Body:
- Digestive enzymes
- Pepsin, trypsin, chymotrypsin break down dietary proteins in the stomach and small intestine.
- Immune system
- Cell cleanup
- The proteasome uses proteases to recycle old or damaged proteins (regulated by ubiquitin tagging).
🧠 Why Proteases Are Important:
| Function | Role |
|---|---|
| Digestion | Break food proteins into absorbable amino acids |
| Cell regulation | Turn enzymes or hormones on/off by cleaving them |
| Apoptosis | Help cells self-destruct when necessary |
| Tissue remodeling | Break down extracellular matrix during growth or healing |
| Pathogen defense | Some proteases fight infections (or are used by viruses to spread) |
💊 Medical Relevance:
- Overactive proteases: Linked to cancer spread (via MMPs), inflammation, tissue damage
- Underactive or misregulated proteases: Can lead to diseases like Alzheimer’s, immune deficiency
- Protease inhibitors: Used as drugs in HIV/AIDS, hepatitis C, and cancer (e.g., ritonavir, bortezomib)
📌 Summary:
Proteases are essential enzymes that “cut up” proteins. They’re vital in everything from digestion and immune defense to cell regulation and death. Like molecular scissors, they need to be precisely controlled — too much or too little can cause disease.