Competitive, Non- competitive, & End- product inhibition by allosteric sites

Competitive inhibitors  Competitive inhibitors – are shaped like the substrates and move into the active sites and prohibit the reaction

Non-competitive inhibitors  Molecules that alter the shape of the active site by binding to the enzyme at a different location and thus altering the shape of the active site…the reaction will not occur

End-product inhibition  Special type of end-product inhibitio is called allostery. Allosteric enzymes are made up of 2 or more polypeptide chains. Activity of allosteric enzymes is regulated by compounds which are not their substrates and which bind to the enzyme at a specific site, well away from the active site. They cause a reversible change in the active site.

 The compounds are called allosteric  effectors and fall into 2 categories: 1.activators – speed up a reaction 1.activators – speed up a reaction 2. inhibitors – slow down a reaction 2. inhibitors – slow down a reaction End products of a metabolic pathway may act as allosteric inhibitors.

EXAMPLE  Phosphofructokinase is an enzyme in glycolysis that produces pyruvate and ATP  When sufficient ATP is produced, it acts allosterically on fructose-1,6-diphosphate in order to stop the ATP production.