Enzymes are a major part of our digestive system, and do the majority of the breaking up of food. There are many different kinds, and they all break up different things, since each one is specialised to a certain food types. They break up particles by placing a particle which is attached to others into the enzyme's active site (an area which is specialised to fit a certain particle, like a key and a lock) and applying pressure onto the particles not in the active site, pushing them away and breaking them up.
However, enzymes will only work at certain temperatures. They work best at body temperature (37 degrees Celcius), but if they are too hot they become denatured and will not break up particles, since their active sites will have melted and remolded. If they are too cold, there is not enough kinetic (movement) energy to put the particles in their active area, so they won't break up food.