Enzymes pp 96 - 102

Enzymes All enzymes are proteins; not all proteins are enzymes. Most enzymes have an –ase ending. ATPase amylase

Enzymes enzyme -

Enzymes Substrate – Enzymes which act on glucose will not act on galactose.

Steps to Enzyme Reactions Write out the 5 steps for an enzyme catalyzing a reaction

Substrate Binding active site Q: What part of AAs interact with substrate? A: R-groups  also involved in the t - negative acid group is attracted to the positively charged part of substrate.

Substrate Binding R-groups

Enzymes activation energy  EA Q: What is an enzyme? A: Biological catalyst; speeds up reactions without being consumed (true for organic and inorganic catalysts) Let’s review the potential energy diagram: 1) Relative energy of reactants and products determine endothermic / exothermic 2) Difference between reactants and transition state = activation energy Q: How does an enzyme change the shape of a potential energy diagram? (refer back to the animation) A: Lowers EA so that more reactions can happen.

Reaction Progression Reaction Progession

Enzyme Energy Enzymes lower the activation energy (EA) of reactions. Enzymes lower EA. Energy stored in the reactants and products don’t change. Therefore, free energy of a reaction does not change. (delta G)

enzyme-substrate complex Substrate Binding induced-fit model - enzyme-substrate complex Enzymes are not static.

Substrate Binding Enzymes reduce EA by:

Enzyme Limitations

Enzyme Limitations

Limitations of Enzymes Why do enzymes operate at an optimal temperature and pH?

Enzyme Limitations cofactors – coenzymes – An apoenzyme is Enzymes don’t always act alone.

Enzyme Inhibition competitive inhibitor – noncompetitive inhibitor – Competitive: estrogen / tamoxifen / BPA example

Enzyme Inhibition

Enzyme Regulation allosteric site – allosteric activator – allosteric inhibitor –

Allosteric Sites Note the two enzyme forms. - identify various allosteric sites - note the different shapes between subunits

Feedback Inhibition A, B, C and D are molecules along a metabolic pathway. E1, E2 and E3 are enzymes required for this metabolic pathway. D is an allosteric inhibitor of E1.