BIOCH 200: Enzymes (February 28, 2014)
• *There are 2 ways of enhancing reaction rate:
o *Adding heat
Not good for biological reactions since excess heat causes
Good for organic chemistry reactions though
o *Adding a catalyst
Most common = enzymes
Other catalysts include certain metals (ex. platinum)
• Enzymes are typically globular (there are exceptions)
o *Globular protein shape lends more functional capabilities
o Enzymes are a catalyst characteristic of biological systems
o *Structure is determined by hydrophobic effects, H-bonding, ionic bonding
(+/- charged amino acids interacting with each other), disulphide bridges
(intramolecular and intermolecular)
o Enzymes are also specific in their function
That being said: Enzyme function is completely determined by their
• Enzymes vs. Non-biological catalysts
o *Enzymes lend higher reaction rates, milder reaction conditions,
greater reaction specificity (while heat can catalyze a lot of different
reactions, enzymes will have a specific reaction that they affect)
o Enzymes are more easily regulated and are important for cooperativity
concerning ligand binding.
• *ALMOST ALL ENZYMES ARE PROTEINS
• Enzymes accelerate reaction rate AND are recovered at the end.
o Increase rxn rate by 10 to 10 x0 • Nomenclature
o *Typically end in “-ase”
o *Typically contain substrate/product name and the chemical reaction.
Ex. citrate synthase enzyme that synthesizes citrate
Ex. alcohol dehydrogenase enzyme that removes hydrogen from
Ex. pyruvate decarboxylase enzyme that removes carboxyl
groups from pyruvate
• Enzymes are regulated.
o Some of this regulation comes from changes in shape which could change
or inactivate a function
• *How do enzymes work?
o *Work by decreasing the activation energy needed for a reaction to
*Stabilizes the transition state by reducing its free energy
*Activation energy is notated: ΔGǂ
• Weird symbol is called: “double dagger”
• *Activation energy = free energy of the transition state - free
energy of the end product.
o I-Clicker information: