Enzymes 2

Enzymes 2

1. Enzyme inhibition

   • Competitive
     • Molecular shape similar to substrate
     • Competes directly with substrate for the active site
     • Malonic acid
     • Occupy the active site in place of substrate
   • Non-competitive
     • Cyanide
       • Inhibits respiration
     • Binds to allosteric site
       • Alters overall shape of enzyme as bonds are affected
         • Substrate no longer complimentary shape
     • No competition for active site

2. Immobilised enzymes

   • Entrapment
     • Enzyme is trapped in gel capsule
       • Alginate beads
       • Beads packed in glass column and substrate is added
         • Reacts with the enzyme as it slowly flows down column
     • No damage to enzyme
   • Adsorption
     • Facilitates contact between enzyme and substrate
       • Enzyme is held by weak forces onto an inert surface
   • Commercial
     • Can be controlled
     • Flows continuously
     • Add or remove enzyme easily
       • Can then be reused
     • Product is not contaminated by enzyme
       • No purification needed
     • Can withstand higher temperatures and wider range of pH levels
     • Slower than free enzymes
     • Entrapment
       • Substrate penetrated beads to access all enzymes, not all enzyme molecules are used

3. Biosensors

   • 1) Blood contains mixture of different molecules
     • 2) Enzyme electrode placed in blood sample
       • 3) Glucose diffuses into immobilised enzyme layer
         • 4) Oxygen is take up
           • 5) Rate of oxygen uptake proportional to glucose concentration
             • Digital display shows accurate concentration of glucose
   • The association of a biomolecule, such as an enzyme, with a transducer, which produces an electrical signal in response to substrate transformation. The strength of the signal may be measured with a meter

4. Properties

   • Substrate specific
   • Fast acting and high turnover number
   • Lowers activation energy

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