Should I drink protein shakes during a juice fast?

I'm preparing to begin a juice fast starting this week, my goal is to also include cardio and weight training during the fast. Will drinking protein shakes after my weight training hinder any progress made during the juice fast? If so are there any protein juice alternatives to the shakes?

I've also read that its best to drink the juice within 30-45 minutes or else some of the beneficial enzymes die off. Can anyone verify that? If its true what's a good way to take juice to work without losing the benefits of the enzymes.