Papain – chemistry, sources, preparation, evaluation, preservation, storage, therapeutic uses and commercial utility MCQs With Answer

Introduction

Papain is a plant-derived proteolytic enzyme (a cysteine protease) obtained primarily from the latex of Carica papaya. This introduction covers papain chemistry, natural sources, extraction and preparation methods, purification and evaluation (activity assays, SDS-PAGE, zymography), and preservation and storage strategies (lyophilization, stabilizers, temperature control). Clinical and therapeutic uses include wound debridement, digestive aids and anti-inflammatory applications, while commercial utility spans pharmaceuticals, food tenderizing and cosmetics. Key formulation and quality-control considerations—enzyme kinetics (Km, Vmax), inhibitors, assay units, shelf-life and regulatory testing—are critical for B.Pharm students studying papain’s pharmaceutical development and industrial applications. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Papain is classified primarily as which type of protease?

• Serine protease
• Aspartic protease
• Cysteine protease
• Metalloprotease

Correct Answer: Cysteine protease

Q2. What is the common botanical source of commercial papain?

• Latex of unripe Carica papaya
• Fermented soybean
• Animal pancreas
• Aspergillus niger fermentation

Correct Answer: Latex of unripe Carica papaya

Q3. Which amino acid residues form the canonical active site triad of papain?

• Ser-His-Asp
• Cys-His-Asn
• Lys-Ser-Glu
• Asp-Ser-Gly

Correct Answer: Cys-His-Asn

Q4. Around which pH does papain exhibit near-optimal activity for most assays?

• pH 3–4
• pH 6–7
• pH 8–9
• pH 10–11

Correct Answer: pH 6–7

Q5. What is the approximate molecular weight of mature papain?

• 8–12 kDa
• 12–15 kDa
• 23–30 kDa
• 50–60 kDa

Correct Answer: 23–30 kDa

Q6. Which assay is commonly used to quantify papain proteolytic activity during quality control?

• Bradford protein assay
• Casein (or azocasein) digestion assay
• HPLC peptide mapping
• UV absorbance at 280 nm

Correct Answer: Casein (or azocasein) digestion assay

Q7. Which of the following is a specific irreversible inhibitor of papain-type cysteine proteases?

• PMSF (phenylmethylsulfonyl fluoride)
• EDTA
• E-64 (epoxysuccinyl peptide)
• Pepstatin

Correct Answer: E-64 (epoxysuccinyl peptide)

Q8. Which additives are commonly used to stabilize papain during storage?

• Glycerol and sugars (e.g., trehalose)
• Sodium chloride and SDS
• PMSF and strong acids
• High concentrations of urea

Correct Answer: Glycerol and sugars (e.g., trehalose)

Q9. For longest shelf-life and retained activity, how is papain most often stored?

• Aqueous solution at room temperature
• Lyophilized powder at low temperature (e.g., -20 °C)
• Neutral buffered solution at 37 °C
• Concentrated in ethanol at 25 °C

Correct Answer: Lyophilized powder at low temperature (e.g., -20 °C)

Q10. Which of the following is a major commercial application of papain?

• Meat tenderizer
• Vaccine adjuvant
• Antibiotic production
• Metal chelation in dialysis

Correct Answer: Meat tenderizer

Q11. In therapeutics, papain is commonly used for which clinical application?

• Antihypertensive therapy
• Wound debridement and proteolytic cleansing
• Systemic anticoagulation
• Antiviral oral rinse

Correct Answer: Wound debridement and proteolytic cleansing

Q12. What pharmaceutical dosage form is papain frequently formulated into for topical use?

• Injectable solution
• Topical ointment or gel
• Inhalation aerosol
• Transdermal patch with sustained delivery

Correct Answer: Topical ointment or gel

Q13. Which kinetic parameter describes the substrate affinity of papain?

• Vmax
• Kd
• Kcat
• Km

Correct Answer: Km

Q14. Which analytical technique is standard for assessing the purity and molecular weight of papain preparations?

• SDS-PAGE electrophoresis
• Gas chromatography
• Polarimetry
• Atomic absorption spectroscopy

Correct Answer: SDS-PAGE electrophoresis

Q15. Commercial papain activity is often reported in which units?

• Milligrams (mg)
• International units (IU) only
• Caseinolytic activity units (e.g., U/mg)
• Mol/L

Correct Answer: Caseinolytic activity units (e.g., U/mg)

Q16. Papain preferentially cleaves peptide bonds adjacent to which type of residues?

• Only acidic residues
• Hydrophobic or basic residues
• Only proline residues
• Only glycosylated residues

Correct Answer: Hydrophobic or basic residues

Q17. Approximately at what temperature does papain begin to show significant thermal denaturation?

• 37 °C
• 50 °C
• 60 °C
• 80 °C

Correct Answer: 60 °C

Q18. What is the primary purpose of lyophilization in papain preservation?

• To concentrate salts
• To remove water and stabilize enzyme activity
• To increase proteolytic activity
• To sterilize the enzyme

Correct Answer: To remove water and stabilize enzyme activity

Q19. Zymography is used in papain analysis to detect what?

• Total protein concentration
• Proteolytic activity of separated proteins in a gel
• DNA contamination
• Lipid content of the sample

Correct Answer: Proteolytic activity of separated proteins in a gel

Q20. Which patient-related concern is most important before topical application of papain?

• History of hypertension
• Allergy to papaya or latex
• Prior antibiotic use
• Presence of metallic implants

Correct Answer: Allergy to papaya or latex

Q21. Which additive chelates metals and can protect papain from metal-catalyzed oxidation?

• SDS
• EDTA
• PMSF
• Hydrochloric acid

Correct Answer: EDTA

Q22. The isoelectric point (pI) of papain is closest to which value?

• pI ~4
• pI ~6
• pI ~9
• pI ~11

Correct Answer: pI ~9

Q23. Which technique is commonly used to screen small-molecule inhibitors of papain in the lab?

• Chromogenic peptide substrate spectrophotometric assay
• Flame ionization detection
• Gel permeation chromatography alone
• Polarography

Correct Answer: Chromogenic peptide substrate spectrophotometric assay

Q24. During purification of papain, which chromatographic method is frequently employed for capture or polishing?

• Ion-exchange chromatography
• Supercritical fluid chromatography
• Gelatin affinity chromatography only
• Steric exclusion only

Correct Answer: Ion-exchange chromatography

Q25. Which step in crude papain extraction primarily removes insoluble debris?

• Dialysis
• Filtration or centrifugation
• Lyophilization
• Gel filtration

Correct Answer: Filtration or centrifugation

Q26. Which preservation method most effectively extends the shelf-life of papain without major activity loss?

• Storage in buffered aqueous solution at room temperature
• Lyophilization with stabilizers
• Heating to 80 °C for sterilization
• Dissolving in concentrated ethanol

Correct Answer: Lyophilization with stabilizers

Q27. Commercial papain preparations are typically standardized by which parameter on labels?

• Mass of powder per gram only
• Activity units per mg (U/mg)
• Volume of solution in mL
• Protein sequence length

Correct Answer: Activity units per mg (U/mg)

Q28. How does papain affect gelatin-based pharmaceutical formulations?

• Increases gel strength
• Has no effect on gel properties
• Hydrolyzes gelatin and reduces gel strength
• Causes polymer cross-linking

Correct Answer: Hydrolyzes gelatin and reduces gel strength

Q29. Which experimental approach helps determine papain substrate specificity?

• Use of synthetic chromogenic peptide substrates with varied residues
• Measuring pH only
• Conductivity measurements
• Elemental analysis

Correct Answer: Use of synthetic chromogenic peptide substrates with varied residues

Q30. For injectable or parenteral papain formulations, which regulatory test is critical prior to release?

• Heavy metal titration only
• Bacterial endotoxin (LAL) test
• pH measurement only
• Visual inspection only

Correct Answer: Bacterial endotoxin (LAL) test

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com