Xanthine oxidase and guanase activities in normal and psoriatic epidermis.

Xanthine oxidase and guanase activities in normal and psoriatic epidermis were demonstrated and accurately assayed by the new micro-assay methods which rely on the isolation of 14C-labelled end-products, xanthine and uric acid, from the substrates, hypoxanthine and guanine, by electrophoresis on cellulose acetate membrane using 0.1 M borate buffer, pH 9.0. The average specific activities of xanthine oxidase and guanase in normal epidermis were 10.2 and 55.0 pmol/min/mg protein, respectively, and in psoriatic epidermis, 52.1 and 980.6 pmol/min/mg protein, respectively. Increased activities of these enzymes in psoriatic epidermis suggested that urate formation might be enhanced in the psoriatic lesions resulting from an increased turn-over of nucleic acids.