why does enzyme activity decrease at high temperatures? Share with your friends Share 1 Manik Mishra answered this Enzymes are proteins. The proteins get denatured at high temperature. Hence, enzyme activity decreases at high temperature. 15 View Full Answer Hunnan Hussain answered this Because, every enzyme has its specific temp. at which they can work, so if we increase the temp. then the enzyme activity will be decreases. -1 Shefali Rockstar answered this because enzymes have an optimum temperature and they denature at high temperature 11