There are, indeed, enzymes in raw foods, but no enzymes in cooked foods, 
due to the excess heat destorying them.

This gives an idea of the various classes of different enzymes that exist:-

http://www.healthboosters.com/archive/digestive_enzymes.htm


http://en.wikipedia.org/wiki/List_of_enzymes

re enzymes/hot weather in other post:- Like I said, enzymes only start getting 
damaged at c.40 degrees celcius, and completely destroyed at c.60 degrees 
celsius. So, on most hot days, enzymes would be unaffected.

Geoff