Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are typically proteins and are essential for various biochemical processes. Enzymes are classified based on the type of reaction they catalyze. Here are the main classes of enzymes with examples:



  1. Oxidoreductases: These enzymes catalyze oxidation-reduction reactions. Example: Cytochrome oxidase, which is involved in the electron transport chain.

  2. Transferases: These enzymes transfer functional groups (such as a methyl or phosphate group) from one molecule to another. Example: Alanine transaminase (ALT), which is involved in amino acid metabolism.

  3. Hydrolases: These enzymes catalyze the hydrolysis of various bonds, breaking down molecules using water. Example: Lipase, which breaks down fats into fatty acids and glycerol.

  4. Lyases: These enzymes catalyze the addition or removal of groups to form double bonds. Example: Aldolase, which is involved in glycolysis.

  5. Isomerases: These enzymes catalyze the rearrangement of atoms within a molecule. Example: Phosphoglucose isomerase, which converts glucose-6-phosphate to fructose-6-phosphate in glycolysis.

  6. Ligases: These enzymes catalyze the joining of two molecules with the simultaneous hydrolysis of a diphosphate bond in ATP or a similar triphosphate. Example: DNA ligase, which is crucial for DNA replication and repair.

Preparation of Papain

Papain is a proteolytic enzyme extracted from the latex of papaya (Carica papaya) fruit. It is used in various industries, including food processing, pharmaceuticals, and cosmetics, due to its ability to break down proteins. Here’s a general outline of the preparation of papain:

  1. Harvesting:

    • Papain is obtained from the latex of unripe papaya fruits. The fruits should be about three months old for optimal enzyme content.

  2. Extraction:

    • The latex is collected by making longitudinal incisions on the surface of the papaya fruit. The latex exudes from these cuts and is collected in a suitable container.

  3. Purification:

    • The collected latex is filtered to remove any impurities like dirt and plant debris.
    • The filtered latex is then subjected to a purification process, which can involve precipitation with ammonium sulfate, dialysis, and chromatography techniques to isolate the enzyme.

  4. Drying:

    • The purified papain is dried to preserve its activity. Freeze-drying (lyophilization) is a common method used, as it maintains the enzyme’s activity by removing water under low temperatures and pressure.
    • The dried papain is then ground into a fine powder.

  5. Standardization and Quality Control:

    • The enzyme preparation is standardized to ensure a consistent activity level. This involves measuring its proteolytic activity using specific substrates and adjusting the concentration as needed.
    • Quality control tests are conducted to ensure the absence of contaminants and to verify the enzyme's activity.

  6. Packaging:

    • The final product is packaged in airtight containers to protect it from moisture and other environmental factors that could degrade the enzyme.

Papain is widely used in the meat industry as a meat tenderizer, in the brewing industry for chill-proofing beer, and in various other applications where protein breakdown is required.