Decreased membrane-bound ATP-hydrolytic activity in psoriatic epidermis*

Previous studies from our laboratory suggested that architectural alterations of the cell membranes may have a major significance in the pathogenesis of psoriasis. Consequently, the membrane‐bound Mg++ activated ATP‐hydrolytic activity was investigated in normal and psoriatic epidermis under the electron microscope. The present study revealed that, in contrast to normal epidermis, only minimal ATP‐hydrolytic activity is present on the cell membranes of psoriatic keratinocytes. This finding may reflect either a diminished attachment of substrate on the altered cell surface or an enzyme defect of the cell membrane. In both cases the reduced interaction between ATP and membrane‐bound ATP‐hydrolysing enzymes represents a functional membrane disorder of the psoriatic keratinocyte, presumably resulting in an insufficient utilization of ATP for active transport mechanisms on the cell surface.