Understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis.
Where the conditions are kept the same or constant.
The temperature are kept the same or constant.
Some animals, mammals as an example, when the environmental temperature either increases or decreases the body temperature remains constant. These are homeothermic organisms and this is a process called thermoregulation. This is an example of homeostatis.
From the rate of reaction to temperature graph, we can tell that there is an optimum temperature of that enzyme in the animal. Which is why the mammals keeps the body temperature at that optimum temperature if possible.