What are the effects of enzyme exposure to high temperatures? [duplicate]

Question

Question: After enzymes are exposed to high temperatures and undergo denaturation, then returned to their optimal temperature and renatured, can the enzyme's active site return to it's original shape and will it function at the same level of efficiency as it did before being denatured and renatured?

Some background I wrote to the question: I am just beginning to learn Cell Biology, I hope what I've written is correct.

When you raise the temperature of an enzyme, at first it will increase the efficiency of the enzyme's activity, but eventually as the temperature rises, the enzyme with stop functioning and undergo denaturation, which means that the 3D formation of the protein is unraveled, so it doesn't function anymore. From what I've managed to research, the high temperature changes the shape of the active site in the enzyme, which is what allows the enzyme's activity in the first place. I know that some proteins cannot be renatured (like adding heat to an egg will fry it and there is no way to unfry it), but some can be renatured (like heated milk, when it cools down the protein bonds will reestablish themselves).

But will the enzyme's active site return to it's original shape and manage to function at the same level of efficiency as it did before? Or is the damage permanent?

Answer 1

The answer is that it completely depends on what specific enzyme you're talking about; some of them will and some of them won't. What you wrote is correct, that increasing temperature of most enzymes (although there are exceptions) will increase their activity to a certain point, after which the proteins lose their 3D structure and become unfolded.

Upon cooling, it all depends on whether the enzyme can re-fold by itself or not. Some proteins when heated form aggregates, which are more stable than the original conformation, and so generally won't refold with cooling. Some proteins are able to fold into proper conformation by themselves, while other require assistance from chaperone proteins in order to fold correctly. Many of these chaperones are called heat-shock proteins, which are upregulated in response to thermal stress. That points to the fact that many proteins can't just refold on their own, and require help to regain their original conformation from these HSPs.

So the real answer is that it all depends on the specific protein. It also depends on how much you heat the enzyme, and how much of its 3D structure you affect, if you only partially denature an enzyme, it's more likely to refold than one that's been completely denatured. However, if you want an answer about enzymes in general, I'd say that most enzymes after denaturation aren't able to refold properly and regain their enzymatic activity, so the damage is permanent.