It seems to be common knowledge that pineapple tenderizes meat. Most sources say that it does so due to proteases (specifically bromelain). However, I've also seen suggestions that acid is an effective tenderizer on its own, and the Wikipedia article on bromelain in the meat tenderizing section says:
Although the quantity of bromelain in a typical serving of pineapple fruit is probably not significant, specific extraction can yield sufficient quantities for domestic and industrial processing.
which is sort of wishy-washy but might mean that there's not actually enough there for tenderizing.
It does seem that pineapple is effective, one way or another. (See for example Will a pineapple marinade reduce a beef roast to paste?)
So what's going on here?
Is the acidity important? Would something equally acidic tenderize just as well? It looks like lemon and lime juice have lower pH than pineapple juice, so how effective are they?
Is the bromelain important? Could you hypothetically neutralize the acidity of pineapple juice and still use it to tenderize, or do you need larger quantities of bromelain extracted for it to be effective?