Cell shedding from human plantar skin in vitro: evidence that two different types of protein structures are degraded by a chymotrypsin-like enzyme.

A recently described endogenous proteolytic process in pieces of human plantar stratum corneum incubated in vitro has been further studied. This process leads to a decrease in cohesion between the cells that had been facing outwards in vivo. Using two methods, that differed with respect to efficiency, to detach surface cells with decreased cohesion, the process could be divided into two steps. The first step took place irrespective of the presence of ethylenediaminetetraacetate (EDTA) and led to a moderate decrease in cohesion between surface cells. The second step occurred only in the presence of EDTA and advanced to a point where the surface cells could be separated from the remaining cohesive tissue pieces by simple agitation. Both degradation steps could be inhibited by aprotinin and chymostatin but not by leupeptin. Zinc sulfate inhibited the first step. The results indicate that there are two different types of protein structures being degraded during the process of cell shedding in vitro. A chymotrypsin-like enzyme may be involved in the process.