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Monday, 8 January 2018




Are biological catalyst that increase the rate of biochemical reactions

The chemical nature of enzymes:

  • Enzymes are proteins 
  • Some enzymes are ribonucleic acids in nature.

General features of enzymes:

  •  Highly efficient: 
  1. Gives 103-108 product per second.
  2. Act at 37°C.
  3. Don’t consumed or changed during the chemical reaction.
  • Specific (reaction and substrate(s))
  1. Absolute specifity (one substrate)
  2.  Reaction specifity (functional group)
  3.  Relative specifity (a group of compounds)
  • Structure of enzyme:
  1. Simple protein
  2. Conjugated protein
Active enzyme =   protein part + non protein part
Holo enzyme         (apoenzyme)         (cofactor)  

Prosthetic group:

  1. Tightly bound to enzyme
  2. Organic (FMN) or metal (Zn, Mg, Mn ,Cu)
  3. Majorly they are metal (metalloenzymes)
  4. Stable

The role of active site :

  • Binding of substrate
  • Catalytic role of the enzyme

Determine the specificity of enzyme Specificity :

  •  Lock and key model
  • Induced fit model

How enzymes increase the rate of biochemical reaction ?

  • Decrease the energy of activation .
  • Equilibrium of reaction
  • Increase attaining to equlibrium but do not affect the equilibrium of reaction.

Classification of enzymes :

  • Oxidoreductases: transfer of electron
  • Transferases       : transfer of groups
  • Hydrolases         : hydrolysis
  • Lyases                : break down of the bonds
  • Isomerases         : convert one isomer to the other
  • Ligases              : formation of C-C, C-N, C-O, C-S

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