Temperature, pH level and concentrations of enzyme and substrate all affect enzyme functionality. Chemical inhibitors can also affect how enzymes function and reduce their effectiveness.
Temperature affects the kinetic energy of any given molecule. Warmer temperatures provide more kinetic energy, increasing the chances for successful molecular collisions. Above an optimal temperature, the enzyme structure starts to break down as molecular bonds are broken and the catalytic activity potential is reduced.
Like temperature, there is also an optimal pH level for enzyme functionality. Changes in pH levels can make or break molecular bonds, changing the shape of enzymes and directly impacting the enzyme's effectiveness.
The rate of reactions catalyzed by enzymes are dependent on the concentrations of enzyme and substrate. The rate of the reaction increases as the concentration of either is increased. The rate of increase grows until the active site is saturated with substrate. If the substrate concentration is high and temperature and pH are kept at a consistent level, the reaction rate is directly proportional to the enzyme concentration.
Chemicals called inhibitors may reduce or even halt the enzyme's catalytic activity. Active site-directed inhibitors occupy the active site and compete with the substrate for the active site. Other inhibitors, called non-active site-directed inhibitors, attach to the enzyme structure and distort its shape.