Originally Posted by Ubercroz
In general... don't do it. (Unless they are a short stack)
The problem is that against their range of AA-JJ and AK you are a 47 to 53 underdog.
However there are some opponents that always shove AA and KK if they are 3-bet thus replacing the 4-bet with a shove, so if you take those hands out of their 4-bet range you are about a 55 to 45 favorite.
It is a pretty thin line and shoving your stack on a 55 to 45 difference is going to be pretty high variance, so get ready to get hit with some pretty bad beats.
That being said it is all about what their range to 4-bet with is, and if you can narrow that down you can make a more correct decision.
We really need to take stack size and pot odds
into account. Depending on the size of the pot, the amount of fold equity we have by 5bet shoving, and the effective stack size amount, getting it in as a 47% dog is +Ev (see pokerkid's post above).
Stakes is a good question - if an unknown at these stakes is ONLY 4betting KK+ (hard for me to imagine, I think AK is common even at 2nl?), it'll have an impact on the math.