THE ROLE OF 2 ENDOGENOUS PROTEASES OF THE STRATUM-CORNEUM IN DEGRADATION OF DESMOGLEIN-1 AND THEIR REDUCED ACTIVITY IN THE SKIN OF ICHTHYOTIC PATIENTS

We investigated the role of stratum corneum (SC) trypsin-like and chym otrypsin-like serine proteases in the degradation of desmoglein-1 (DSG -1) in the SC sheet. DSG-1, whose presence in the SC sheet was confirm ed by Western blot analysis, was degraded completely during incubation of the SC sheet in Tris buffer. The degradation of DSG-1 was inhibite d by the addition of protease inhibitors, such as aprotinin or a mixtu re of leupeptin and chymostatin. Either leupeptin or chymostatin alone did not inhibit its degradation. These results indicated that both tr ypsin-like and chymotrypsin-like serine proteases are involved in the degradation of DSG-1. We further examined the activities of the two pr oteases in the SC obtained from patients with ichthyosis vulgaris, in whom SC desquamation is abnormal. The enzymatic activities measured us ing synthetic substrates were significantly decreased in these ichthyo tic SC samples. This result supports the idea that these proteases pla y an important role in normal SC desquamation.