Th1L07 Enzymes

Th1L07 Enzymes

1. Main properties

   • biological catalysts
   • speed up the rate of the reaction
     • reduces necessary free energy (delta G) need to overcome the activation energy
   • do NOT alter final equilibrium b/w reactants and products
   • proteins
     • Dependent on many weak bonds e.g. hydrogen bonds, electrostatic salt links and hydrophobic interactions
       • Makes enzymes sensitive to changes in their environment
         • Inactive enzyme
           • Denatured enzyme state
         • e.g. by eating the protein, giving rise to a disorganised or tangled structure in which the enzyme no longer has any catalytic activity
         • temperature
           • Between 20C, 30C and 40C for enzymes found in the body, you will usually speed up the reaction
           • Up to 50C and beyond, denaturing of the protein will occur, similarly going to far below 20C will also reduce reaction velocity

2. Enzyme catalysis

   • Enzymes contain an active site
   • substrate binds to the enzyme at the active site producing an enzyme-substrate complex
   • enzyme is then disregarded at the final product is revealed
   • Stickase metaphor
     • illustrates that enzymes should be complementary to the substrates transition phase rather than the substrate itself to bring about the activation of the reaction > product

3. Substrate specificity

   • catalyse only one type of reaction and will act only on a few related molecules ('Group...')
     • few are so specific that they will act only on a certain enzyme even to the point will it will only act on one stereoisomer
   • presence of a groove or cleft of defined shape called the active site into which only the substrate of the correct shape and charge can fit
   • Relevance?
     • multiple enzymes within the same cellular compartment can co-exist without interfering with e/o
       • allows for multiple metabolic pathways w/i cells
   • Systematic classification scheme of 6 main classes
     • Six classes are divided into subgroups according to their substrate or source i.e. the type of reaction they catalyse                               
     • Each enzyme IDed by individual 4 digit number        I.U.B. Commission on Enzymes - established the systematic classification on enzymes           Catalase 4 digit classification code - E.C. 1.11.1.6.          
     • mnemonic: TO HILL
       • transferase
       • oxoreductase
       • hydrolyase
       • isomerase
       • ligase
       • lyases

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