Something I always think of when I am dumping all that hot water on those cool grains is the effect it might be having on them.
Not the whole grist but the part that is in contact with the hot water at the start.
Something worth thinking about anyway.
Essentially, even at 180F, the enzymes do not denature "instantly". Yes, some will, but because only a small percentage of the grist is subjec to the temperature for such a short time, my intuition is that there is not much to worry about. If you do denature a quantity of enzymes, then you just have to let the mash go a little longer before full conversion. If you denature a disproportionate amount of Alpha vs Beta amalyse, then adjust your mash temperature up or down to compensate.
In the end, if you are producing the kind of wort you want, then relax and have a homebrew
! If not, then just compensate with time or temp.
Also, I know that there are some "pro brewer's" papers that have been written about enzymes and the half lives at different temperatures. If you are looking for some hard data, then looking one of those up may be your answer.