Pepsin – chemistry, sources, preparation, evaluation, preservation, storage, therapeutic uses and commercial utility is a concise guide for B.Pharm students exploring this important gastric proteolytic enzyme. Pepsin is an aspartic endopeptidase (≈34 kDa) derived from pepsinogen, with optimal activity at pH 1.5–2 and specificity for peptide bonds near aromatic residues. Key topics include common sources (porcine, bovine gastric mucosa), extraction and activation of pepsinogen, purification methods (salt fractionation, chromatography), activity assays (casein/hemoglobin/Anson methods), stability, preservation (lyophilization, antioxidants), storage conditions, therapeutic applications as digestive aid, and broad commercial utility in pharmaceuticals, food and leather industries. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary catalytic mechanism class of pepsin?
- Serine protease
- Cysteine protease
- Aspartic protease
- Metalloprotease
Correct Answer: Aspartic protease
Q2. From which precursor protein is active pepsin produced?
- Propepsin
- Pepsinogen
- Preproenzyme
- Zymogen A
Correct Answer: Pepsinogen
Q3. What is the typical molecular weight of mature pepsin A?
- 10 kDa
- 34 kDa
- 60 kDa
- 90 kDa
Correct Answer: 34 kDa
Q4. Which animal source is most commonly used for commercial pepsin production?
- Human gastric tissue
- Porcine gastric mucosa
- Chicken pancreas
- Fish liver
Correct Answer: Porcine gastric mucosa
Q5. What pH gives optimal activity for pepsin?
- pH 7.4
- pH 5–6
- pH 1.5–2
- pH 9–10
Correct Answer: pH 1.5–2
Q6. Which reagent is a specific inhibitor of aspartic proteases like pepsin?
- PMSF (phenylmethylsulfonyl fluoride)
- EDTA
- Pepstatin A
- E-64
Correct Answer: Pepstatin A
Q7. Which assay is classically used to measure pepsin activity by hydrolysis of a protein substrate?
- Bradford protein assay
- Anson (hemoglobin/casein) assay
- ELISA for pepsin antigen
- Folin–Ciocalteu assay
Correct Answer: Anson (hemoglobin/casein) assay
Q8. Activation of pepsinogen to pepsin primarily requires which condition?
- High salt concentration
- Low pH (acidic environment)
- High temperature (80°C)
- Alkaline buffer
Correct Answer: Low pH (acidic environment)
Q9. Which chromatography method is commonly used for pepsin purification?
- Size-exclusion chromatography
- Affinity chromatography for His-tag
- Ion-exchange chromatography
- Gas chromatography
Correct Answer: Ion-exchange chromatography
Q10. For pharmaceutical preparations, which preservation method best retains pepsin activity long-term?
- Storage in aqueous solution at room temperature
- Lyophilization (freeze-drying)
- Boiling then refrigeration
- Spray pyrolysis at high heat
Correct Answer: Lyophilization (freeze-drying)
Q11. Which factor most strongly accelerates irreversible denaturation of pepsin?
- Mild acidic pH
- Moderate cooling to 4°C
- High temperatures (>50°C)
- Presence of glycerol
Correct Answer: High temperatures (>50°C)
Q12. Pepsin preferentially cleaves peptide bonds adjacent to which type of amino acid residues?
- Basic residues (Lys, Arg)
- Aromatic residues (Phe, Tyr, Trp)
- Sulfur-containing residues (Cys, Met)
- Small residues (Gly, Ala)
Correct Answer: Aromatic residues (Phe, Tyr, Trp)
Q13. Which of the following is a standard quality control test for pepsin preparations?
- Antimicrobial susceptibility testing
- Enzyme activity (specific activity) assay
- DSC calorimetry only
- Blood coagulation time
Correct Answer: Enzyme activity (specific activity) assay
Q14. In formulation, which excipient can stabilize pepsin during storage?
- Strong oxidizing agents
- Reducing sugars causing Maillard reaction
- Polyols like glycerol or trehalose
- High concentrations of proteases
Correct Answer: Polyols like glycerol or trehalose
Q15. Therapeutically, pepsin is most appropriately used as:
- An antihypertensive agent
- A topical antiseptic
- A digestive enzyme to aid protein digestion
- An antiviral agent
Correct Answer: A digestive enzyme to aid protein digestion
Q16. Which storage temperature is generally recommended for lyophilized pepsin to maintain activity?
- -20°C to -80°C
- Room temperature (20–25°C)
- 40°C incubator
- Boiling water bath
Correct Answer: -20°C to -80°C
Q17. During commercial production, initial extraction of pepsin from gastric mucosa commonly uses which solvent condition?
- Neutral aqueous buffer pH 7.0
- Basic solution pH 9–10
- Cold acidified aqueous solution (e.g., HCl)
- Organic solvents like chloroform
Correct Answer: Cold acidified aqueous solution (e.g., HCl)
Q18. Which analytical technique helps determine purity and subunit size of pepsin?
- SDS-PAGE electrophoresis
- UV-visible spectroscopy at 600 nm
- Polarimetry only
- pH titration curve
Correct Answer: SDS-PAGE electrophoresis
Q19. In the food industry, pepsin is used primarily for:
- Flavoring agents synthesis
- Milk clotting for cheese production
- Protein hydrolysis to produce peptides and flavors
- Carbonation of beverages
Correct Answer: Protein hydrolysis to produce peptides and flavors
Q20. Which USP parameter is critical for enzyme preparations like pepsin?
- Potency expressed as activity units per mg
- Melting point range
- Specific rotation only
- Conductivity at 25°C
Correct Answer: Potency expressed as activity units per mg
Q21. One common unit of pepsin activity is defined based on hydrolysis of which substrate?
- Glucose
- Casein or hemoglobin
- Lipids
- DNA
Correct Answer: Casein or hemoglobin
Q22. Which preservative approach is least suitable for pepsin in liquid pharmaceutical formulations?
- Adding antimicrobial agents and cold storage
- Adjusting to acidic pH compatible with activity
- Inclusion of protease inhibitors
- Prolonged storage at room temperature without stabilizers
Correct Answer: Prolonged storage at room temperature without stabilizers
Q23. Which safety consideration is important for handling crude pepsin preparations?
- Risk of enzyme-induced dermal sensitization or irritation
- No precautions needed—completely inert
- Highly radioactive contamination risk
- Explosive hazard on contact with air
Correct Answer: Risk of enzyme-induced dermal sensitization or irritation
Q24. Which manufacturing step helps remove low-molecular-weight impurities from pepsin extract?
- Dialysis or ultrafiltration
- Heating to 100°C
- Adding strong oxidizers
- Drying at high pH
Correct Answer: Dialysis or ultrafiltration
Q25. Pepsin activity declines rapidly above which pH due to loss of catalytic aspartic acid protonation?
- pH 2–3
- pH 4–6
- pH 7–9
- All pH values equally active
Correct Answer: pH 4–6
Q26. In pharmaceutical enzyme formulations, what is the advantage of microencapsulation of pepsin?
- Immediate enzyme denaturation
- Improves stability and controls release in GI tract
- Eliminates the need for cold chain
- Converts pepsin into an inactive prodrug
Correct Answer: Improves stability and controls release in GI tract
Q27. Which industrial sector besides pharmaceuticals and food commonly uses pepsin?
- Textile bleaching
- Leather processing and tanning
- Fertilizer manufacturing
- Petroleum refining
Correct Answer: Leather processing and tanning
Q28. What is a critical label requirement for commercial pepsin preparations?
- Expiration date and storage conditions
- Manufacturer’s social media handle
- Recommended cooking recipes
- Color preference of the powder
Correct Answer: Expiration date and storage conditions
Q29. Which kinetic property is commonly determined for enzymes like pepsin during evaluation?
- Km and Vmax with a chosen substrate
- Nucleotide sequence analysis
- Boiling point elevation
- Optical density at 700 nm only
Correct Answer: Km and Vmax with a chosen substrate
Q30. When formulating tablets containing pepsin, which excipient consideration is most important?
- Use of oxidizing binders to enhance activity
- Avoiding incompatible protease inhibitors and extreme pH excipients
- Inclusion of strong acids to increase loss of activity
- Maximizing water content in tablet core
Correct Answer: Avoiding incompatible protease inhibitors and extreme pH excipients
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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