Changes in temperature and pH alter the structure and substrate binding of enzymes, which affect their properties and activity. Every enzyme has an optimal temperature and pH at which it works at maximum efficiency. At higher temperatures, enzyme activity generally increases but only up to a certain temperature. Temperatures higher than a certain point may cause denaturation and inactivation of the enzyme. With regards to pH, any deviation from the optimum pH level for that enzyme can reduce its activity. As the pH level moves further away from the optimal point, it can cause the enzyme to become completely inactive.