Add the enzyme in the mash, shoot for a mash temp of 143 - 146 to not denature the enzyme. The equivalent of 20mls / 100#s of grain is enough. Add the enzyme 1/3 of the way into mashing to ensure the mash isn't too hot to denature the enzyme. Stir very well and let the mash have an hour-long rest to let the enzyme do its work."
"The other option would be to add the enzyme to the kettle while lautering, then hold off on heating the kettle until all wort is in and has 30 minutes of contact with the enzyme at around 145 degrees (lower would be fine, too)."
"I know a lot of homebrewers just throw grain on top of all their mash water, so this option makes more sense to them. I preferred not to mash this way, when I was a homebrewer... I think the conversion temp is more consistent adding grain and water at the same time, I also like being able to react to the consistency so I can end up the thickness I want."
"The enzyme will denature in the boil, but it's already done its work."
"That would all mean that the amylo in the fermentation is no longer needed. I'm finding better results with fermentation character and hop aromatics by having no enzyme present in the fermentation."
Lastly, it is very important to add nutrient to the boil as well as 1/2 way through fermentation (with something like BSG's Startup) since the wort will be almost entirely glucose, there is not a lot of nutrition for the yeast.
