ENZYMATIC-ACTIVITY OF DESQUAMIN

We have previously described the properties of desquamin, a cell adhes ion molecule in the stratum corneum with lectin-like properties specif ic for amino sugars. We report here that desquamin is also a trypsinli ke serine proteinase. It degrades several chromogenic peptides with ar ginine in the P1 position, with greatest activity for the tissue plasm inogen activator peptide; it has no chymotrypsin-like activity. The en zymatic activity of desquamin is inhibited by aprotinin, leupeptin, an d soybean trypsin inhibitor. The K-m for all active substrates is in t he millimole range and the pH for optimal activity is near 10. The enz ymatic activity is stable in the temperature range from 37 to 80 degre es C, peaking near the upper end; it is only partially inhibited at 10 0 degrees C. Using zymogels with immobilized substrates, we show that desquamin degrades both casein and human keratins. Because desquamin i s localized to the lipid envelopes of the stratum corneum and can func tion as an enzyme (and is extremely resistant to chemical and thermal degradation), it is in a position to play a crucial role in desquamati on. (C) 1994 Academic Press, Inc.