Puzzling cooking issue: Beer and burgers?

I just made beer burgers for the first time the other night using a simple, self made recipe: soak the burgers in beer (Heineken), toss onto skillet. Simple, easy. But something happened that I didn't expect: when I poured the beer into a bowl containing the ground beef, the beer seemed to break the meat down almost instantly, making it difficult to form the meat into patties, and even more difficult to keep it from falling apart while cooking it. I am just curious as to what would cause this... and does this reaction break down the meat itself, or does it break down the fat in the meat? Thanks a bunch!