Enzyme Regulation Chapter Biochemical Pathways Regulations of Enzymes Objective: I can identify and describe the different ways enzymes are regulated, based on what molecules are binding where.

Enzyme Regulation How the cell affects enzyme activity “on purpose”  regulate activity Send “signal molecules” to bind to enzyme: activate or repress 1) Can bind to active site (prevent substrate binding): only repress 2) Can bind “elsewhere” to change enzyme shape (to allow or to prevent substrate binding): activate or repress Allosteric enzymes: can change to other shape (not by substrate)

Signal Molecules Activation – “activator molecule”s Primes enzyme to catalyze (increase rate) Cofactor: inorganic molecules that bind Coenzyme: organic molecules that bind Vitamins are coenzymes Cooperativity: substrate itself increases rate Inhibition – “repressor molecules” Competitive – binds to active site Noncompetitive – binds to allosteric site Not all enzymes are allosteric/have allosteric site “elsewhere” that causes enzyme to change shape

Allosteric Enzyme Regulation Repressor signal molecule Will change shape so CANNOT bind Activator signal molecule Will change shape so CAN bind Where come from? Active Site Allosteric Site

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Feedback Inhibition System of enzyme regulation where product of reaction can be signal molecule (inhibition  repressor) Competitive feedback inhibition Product binds directly to active site Noncompetitive feedback inhibition Product binds to allosteric site Allows for self-regulation If too much product, stops catalysis (repress) If too little product, continues catalysis Binding not permanent (can diffuse away) Product

Biochemical Pathway A “chain” reaction Involves several enzymes (closeby) Product of one catalyzed reaction becomes substrate for next Desired product only made at end of pathway Similar to Assembly Line Allows for more precise control