Enzymes Part II: Factors that Affect Enzymes

Factors that Affect Enzyme Activity (Rate of Reaction) : 1.Environmental Conditions 2.Cofactors and Coenzymes 3.Enzyme Inhibitors 4.Enzyme Concentration 5.Substrate Concentration

1. Environmental Conditions A. Effect of Temperature Speed of reaction increases until an Optimum temperature is reached Optimum temperature is the temperature at which the enzyme works best After this point the rate of reaction decreases until there is no reaction At this point enzyme is said to be DENATURED – active site destroyed High temperatures are the most damaging to proteins/enzymes. (Cooking denatures proteins)

1. Environmental Conditions A. Effect of Temperature Optimum temperature can be determined by graphing enzyme activity vs. T The peak indicates the optimum temperature of the enzyme.

1. Environmental Conditions A. Effect of Temperature Optimum temperature can be determined by graphing enzyme activity vs. T Which enzyme is more likely to be found in the human body? Enzyme AEnzyme BEnzyme C

Most enzymes have an optimum pH of 7 H+ and OH- ions affect bonding b/w R groups = CHANGES THE SHAPE OF THE ENZYME!!!!! Some enzymes have a different optimum pH –Ex. pepsin (protease in stomach) has an optimum pH of 2 –Why do you think pepsin’s optimum pH is 2? 1. Environmental Conditions B. Effect of pH

Optimum pH can be determined by graphing enzyme activity vs. pH The peak indicates the optimum pH of the enzyme.

1. Environmental Conditions B. Effect of pH Optimum pH can be determined by graphing enzyme activity vs. pH What is the optimum pH of: Pepsin? Amylase? Trypsin?

1. Environmental Conditions C. Effect of Ion concentration (salts) High ion concentrations can affect the charge of R side chains in proteins and enzymes The changing shape changes the enzyme’s activity.

Optimum ion concentration can be determined by graphing enzyme activity vs. ion concentration What is the optimum ion concentration of this enzyme? 1. Environmental Conditions C. Effect of Ion concentration (salts)

2. Cofactors and Coenzymes A. Cofactors Inorganic substances such as atoms of zinc, iron, or copper Affect enzyme activity. Enzyme might not work without them! B. Coenzymes If the cofactor is an organic molecule. Usually made from vitamins

2. Cofactors and Coenzymes Gold, Iron, Zinc, Calcium ions, etc. Vitamins, and other organic molecules

C. Enzyme Inhibitors inhibitor - a chemical that interferes with an enzyme’s activity. A. Competitive Inhibitor - resembles normal substrate - competes for the active site - Blocks the substrate from entering and thereby prevents the enzyme from acting.

B. Non-competitive inhibitors Does not enter the active site Instead binds to enzyme somewhere else. Changes the shape so the substrate no longer fits

Competitive vs. Non-competitive inhibitor graph Eventually, the substrate outnumbers the competitive inhibitor But the non-competitive inhibitor will always lock up the same amount of enzyme

4. Enzyme Concentration When substrate concentration is in excess amounts the concentration of enzyme limits the reaction speed

4. Enzyme Concentration But eventually, the is not enough substrate for the enzyme to GO ANY FASTER!

5. Substrate Concentration As more substrate is added… eventually a saturation point is reached