Plasminogen activator and histone hydrolyzing proteases in psoriasis scales--possible role in increased cell division.

Psoriatic plaque scale was collected from untreated patients, homogenized, and subjected to chromatography on Sephadex and DEAE-cellulose to separate proteolytic enzymes. Five proteolytic enzymes were partially separated and characterized as to their substrate specificities, pH-optimum and inhibitor characteristics. A neutral trypsin-like protease, an alkaline histone hydrolyzing protease and a neutral chymotrypsin-like protease isolated were found to differ from those separated earlier from normal human skin using the same procedures for enzyme purification. The trypsin-like enzyme preparation was found to be an effective fibrinolytic activator and the histone hydrolyzing enzyme showed fibrinolytic activity. The possible roles of these proteases in the increased cell division rate of psoriatic plaque are discussed.