PURIFICATION AND PRELIMINARY CHARACTERIZATION OF STRATUM-CORNEUM CHYMOTRYPTIC ENZYME - A PROTEINASE THAT MAY BE INVOLVED IN DESQUAMATION

In recent work we have shown that a serine proteinase, stratum corneum chymotryptic enzyme, with properties compatible with a role in desqua mation in vitro as well as in vivo, is generally present in human stra tum corneum. The enzymologic properties of the stratum corneum chymotr yptic enzyme in a KCl extract of dissociated plantar corneocytes were compared with those of other known chymotryptic serine proteinases. St ratum corneum chymotryptic enzyme was found to differ significantly fr om bovine chymotrypsin, human cathepsin G, and human mast cell chymase s in regard to inhibitor profile and substrate specificity. Stratum co rneum chymotryptic enzyme was further purified from KCl extracts of di ssociated plantar corneocytes by affinity chromatography on gels with covalently linked soybean trypsin inhibitor. The purified preparation contained one major component with apparent molecular weight 25 kD and one minor component with slightly higher apparent molecular weight as revealed by Coomassie staining after electrophoresis in polyacrylamid e gels with sodium dodecyl sulphate of samples that had not been reduc ed. Both these components were associated with chymotrypsinlike activi ty as revealed by zymography in polyacrylamide gels with co-polymerize d casein. On zymography gels, the purified preparation was also found to contain minor amounts of components with trypsinlike activity. The major purified protein had an apparent molecular weight of around 28 k D after reduction and full denaturation and was shown to contain carbo hydrate.