Factors Affecting
Enzyme Activity
Temperature, pH, cofactors/coenzymes,
enzyme concentration
Temperature
O Enzymes are very sensitive to changes in
temperature
O If the temperature is too high or too low, the
rate of the reaction will be altered
Ex. Canning food through
heating keeps the food from
spoiling
O If oC is too high  bonds in the enzyme are
too weak to hold substrate in the proper
position
O If oC is too low  the bonds that allow for
induced change in shape are too rigid
Optimal Temp
Beyond the critical
temperature point, the
enzyme is denatured 
change in shape
leaving it inactive
(total function loss)
pH
O Every enzyme has an optimal pH in which it
works best
O Pepsin (digestive enzyme in stomach) 2
O Trypsin (digestive enzyme in small intestine) 8
Optimal pH
Amylase: Enzyme breaks down starch in your mouth, is denatured in the
stomach and has to be re-released in the intestine for further degradation
Cofactors/Coenzymes
O Small molecules from minerals & vitamins
 bind to the substrate OR the active site and
can be required for the enzyme to function
O Cofactors (inorganic) ex. Ca2+, Zn+, K+ (ions)
O Coenzymes (organic, nonproteins) ex. ATP, NAD+,
vitamins
*some simply provide the + or – charge to the active site
that allows for electrostatic attraction
Enzyme concentration
http://www.youtube.com/watch?v=Mgw6ZjiiGa0