[Marija]

I've been searching through this forum and (of course) "google-ing" the web, but I can't seem to find an answer to my question:

I've read about this enzyme (acetylcholinesterase) and I understand that it's catalytic site is actually a catalytic triad (Ser, His, Glu). But I have problems with understanding the term "peripheral anionic site (PAS)" of this enzyme in question. I found out (on the web) that it is an allosteric site of acetylcholinesterase, but I'm not sure how it works. What's the "mechanism" of it's allosteric function?

Could anybody please help? I'd really appreciate it.