Enzymes I

Nota:

• Low temperature, neutral pH, atmospheric pressure, aqueous environment

1. Active site

Nota:

• A separate binding site determines the specificity of serine proteases.
• Chymotrypsin - large hydrophobic substrates Trypsin - (+) substrates Elastase - small substrates (glycine)

1. Due to conformation
   1. Active site
      1. Where substrate binds
2. Stereospecific

1. Coenzymes

   Nota:

   • Non-protein parts of the enzymes
   1. Vitamins

      Nota:

      • Vitamins are precursors to coenzymes
      1. Thaimin (B1)
         1. Thiamine pyrophosphate
            1. Aldehyde transfer
               1. Covalent intermediate w/ keto groups
            2. deficiency
               1. Beriberi
      2. Riboflavin (B2)
         1. Flavin Adenine Dinucleotide (FAD)
            1. Redox
            2. Deficiency
               1. Cheliosis and angular stomatitus, dermatitus
      3. Pyridoxine (B6)
         1. Pyridoxal Phosphate
            1. Group transfer to/from AAs
               1. Covalent complexes w/ amino groups
            2. Deficiency
               1. Depression, confusion, convulsion
      4. Nicotin acid (niacin)
         1. Nicotinamide adenine dinucleotide (NAD+)
            1. Redox
            2. Deficiency
               1. Pellagra
            3. Used by alcohol dehydrogenases to abstract H from alcohols

1. Oxidation-reduction
   1. lactate dehydrogenase

1. Group transfer
   1. NMP Kinase

1. Hydrolysis Rxns
   1. Chymotrypsin

      Nota:

      • Mechanism of Chymotrypsin: First, the subtrate binds.
      • Next, histidine activates serine for nucleophilic attack.
      • After that, the oxyanion tetrahedral intermediate is stabilized by H-bonds.
      • Then, the cleavage of the peptide bond occurs.
      1. Serine protease
         1. Hydrolyzes peptide bonds

1. Addition/removal of groups to form double bonds
   1. Fumarase

1. Isomerization
   1. Triose phosphate isomerase

1. Ligation of two substrates at the expense of ATP hydrolysis
   1. Aminoacyl-tRNA synthetase

1. Induced fit model