Enzyme Overview
Overview
enzyme characteristics
- Increase rate of reaction by lowering activation energy
- Most are proteins
- Specific – conversion of one specific substance to one product
- May require cofactors or coenzymes
- Carefully regulated
delta G = free energy
- Free energy of the product minus the free energy of the reactants
- delta G is negative for enzymatic reaction because energy is released (exergonic reaction)
delta Ea = activation energy
- Energy barrier that must be overcome for a reaction to proceed
- Enzymes lower activation energy of a reaction by stabilizing transition state
- Energy required to get to equilibrium (rate of forward and reverse reactions are the same) correlates with ?G and is unchanged in the presence or absence of enzyme
- Enzyme doesn't dictate whether reaction will proceed but determines speed of reaction
ENZYME ACTIVE SITE
- 3D structure produces active site
- Shaped so that substrate fits in
- Product of an enzymatic reaction has lower affinity for binding site: exits binding site and is released
COFACTORS AND COENZYMES
- Bind cofactor binding site (distinct from active site)
- Some enzymes inactive without cofactor or coenzyme
- Many are vitamin-derived, metal ions, or other smaller organic molecules