optimum pH of amylase from sweet potato is about 6.0

The optimum temperature for pepsin is between 30 degrees Celsius and 40 degrees Celsius. Activity has been reported outside of this range.

The optimum temperature for the enzyme polyphenol oxidase (PPO) is 40 degrees Celsius. This is the temperature at which the enzyme is most effective; like many other enzymes the rate of reaction will decrease with temperature, but if the temperature rises much above the optimum level, it will cause the enzymes to denature. Denatured enzymes will stay denatured even if the temperature decreases again. The optimum pH for polyphenol oxidase is 5.

The optimum temperatre like the optimum pH is the temperature at which the protein funcions most effectively. At too low a temperature the reaction kinetics do not allow for a fast reaction and at too high a temperature the enzyme changes it shape and so no longer accepts the substrate so easily. It is often assumed that proteins have and optimum temperature of 37 degrees C as this is the core body temperature of a human being. But this is only for the majority of proteins as many have a much higher or lower optimum temperature.

Most cells operate around a pH of 7.4