Cutaneous sialidase

A fluorometric microassay is described for sialidase using the natural substrate sialyllactose. This technique has been used to characterize and quantify cutaneous sialidase. The enzyme was found exclusively in the particulate fraction of skin homogenates. Its properties were similar to those from other mammalian tissues, showing a pH optimum of 4.0 and a Km of 0.47 mM. Although the modal value of levels in psoriatic biopsies was similar to normal, a few specimens contained exceptionally high activity.