what is the affect of temperature and pH on enzyme activity?

enzymes are pH specific, that is, they have an optimal range in which they will work. if you deviate too far outside either over or under the range, the enzyme will decrease in activity and eventually denature and stop working.

With temperature, enzyme activity increases exponentially until the temperature reaches a high enough point at which the enzyme denatures, and thus again no activity after denaturation

Temperature affects enzymes in two ways. In lower temperatures, the molecular energy is reduced, thus slowing down the rate of reaction. In higher temperatures, the enzyme's structure can actually be changed, and seeing enzymes are very specific to their reaction, will make the enzyme not function. On graphs, with temperature as the independent variable, You often see a slow rise in reaction rate as temperature increases, then suddenly falls. This explains this. Don't have any specific things for PH. Sorry.

The higher the temperature and lower pH the faster the enzyme reacts.

The lower the temperature and higher pH the slower the enzyme reacts.