The activity of enzymes is mainly dependent on its active site. The active site is form from secondary and tertiary proteins. Secondary or tertiary proteins are characterised by helical or folded structure.
The enzymes are active at optimum temperature and optimum radiation only. At high temperatures or in presence of UV rays, the enzymes become inactive or denatured. This is because , at high temperature or in presence of UV light its shape of active site is disturbed due to unfoldind and uncoiling of protein strands. This happens because of breaking of weak bond in between the stands of proteins. So, secondary and tertiary structure is disturbed making it inactive or denatured.