Not sure exactly what you mean by degrade or impure. Essentially what you are getting at is that chirality of any organic molecule which can be denoted as R or S. The human body almost always prefers R. (The naming doesnt really mean much, it's a lesson in stereochemistry which is the spatial relationships of side functional groups the carbon center.) S-ALA has been speculated to be neutral or actually adverse to the human body. That's why companies (not just in the ALA business) spend tons of $ making sure they have just R chirality in their compounds.
I may be answering the wrong question here, so feel free to ask again if I did just this.
Some people are quick to say it doesnt matter what you get (i.e. - buying generic ALA) but I am fairly convinced that R-ALA is the way to go. K-R-ALA is simply a salt form of R-ALA attached to K (Potassium). I have yet to read more about this further modification.
Higher Power has always worked fine for me, so I would not worry right now.