Enzymes

n Catalytic proteins n Catalyst - a chemical agent that changes the rate of reaction, without being consumed by the reaction

Free energy of activation n Initial investment of energy to start a reaction n Energy used to break the bonds in the reactant n Activation energy = E A

Enzymes Lower Activation Energy

Active Site - Catalytic region n Lowers the Ea in a variety of ways –Provides a template for orientation of the substrate –Changes the substrate, stressing critical bonds –Provides correct microenvironment

Active Site

Substrate Specificity n Uniquely shaped active site determines the particular substrate that can be acted upon n Induced fit - binding of the Enzyme to Substrate causes a slight change in shape of the Enzymes

Induced Fit

Environmental effects n Environment can influence 3-D structure of the protein (enzyme) i.e. adding H 2 SO 4 denatures the enzyme n Each enzyme has optimum conditions for pH and temp

pH and Temperature effects

Cofactors n Nonprotein ions or organic molecules (coenzymes) n Required for the proper function of some enzymes –NADH –Coenzymes –Vitamins –Metals

Cofactors Metal Ion Changes the active site shape

Inhibitors n Selectively reduce Enzyme function n Competitive –Structurally similar to Substrate –Competes for active site binding

Competitive Inhibitors

n Noncompetitive –Binds to a place other than the active site –Disrupts Enzyme’s shape or function

Non-Competitive Inhibitor

Allosteric Interaction-Inactivator

Allosteric Interaction- Activator

Regulatory molecules n Activator (increases rate) n Inhibitor (decreases rate) n Binds to allosteric sites = noncatalytic sites that alter the Enzyme conformation/function