Commercial meat tenderizers often contain papain, a proteolytic (protein-digesting) enzyme derived from papayas. how might such products make meat more tender?

A protein digesting enzyme would make meat more tender by breaking down long fibrous protein chains into shorter protein chains. Just as piercing a tough piece of meat many times with a thin blade will cut long protein fibers into shorter, more tender fibers, an enzyme will do the same type of cutting, but on a microscopic level.