How do you prevent enzymatic browning?

Add salt or sugar solution.

Water with a Vitamin C tablet dissolved in it works the best. Trust me, I did an experiment on it once.

you can prevent an apple from browning by adding lemon juice to it

You can always spray or brush it with lemon juice. I always to the cut apple into a lightly salt water right after cutting it. This will keep the cut apple from browning.

Temperature does affect enzymatic function - temperature affects the "active site" of the enzyme and so the substrate cannot bind to it anymore (process is called denaturation)