Action of Neuraminidase on Human Kidney Alkaline Phosphatase

Abstract

STARCH-GEL electrophoresis and chromatography on substituted cellulose ion-exchangers have demonstrated that extracts of human kidney contain more than one protein possessing alkaline phosphatase activity. Similar patterns of distribution of enzymatically active zones after starch-gel electrophoresis have been obtained by several workers^1,2 and three distinct zones can often be demonstrated : a single zone migrating rapidly towards the anode (Fig. 1, zone 1), a second broad, heterogeneous component (Fig. 1, zone 2), and a third band which migrates very slowly and which may represent enzyme bound to lipid material (Fig. 1, zone 3). The first rapidly migrating component cannot be demonstrated in all extracts, but may sometimes appear after storage at −15° for some months. Elution patterns of kidney alkaline phosphatase from DEAE-‘Sephadex’ columns exhibit a broad similarity, but here also there is some variation from extract to extract. A common feature of all such chromatograms, however, is a sharp peak of activity appearing first in the effluent (Fig. 2). The elution pattern of the remaining enzyme is more varied, but often a second fairly broad peak is obtained³. The presence of sialic acid groups is known to increase the electrophoretic mobility of proteins⁴, and Robinson and Pierce⁵ have demonstrated that, after treatment with neuraminidase to remove sialic acid, the electrophoretic mobility of certain alkaline phosphatase components was reduced. To investigate whether the binding of sialic acid is in any way related to the heterogeneity of kidney alkaline phosphatase, this enzyme has been treated with neuraminidase.