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ARYLSULPHATASES IN HUMAN BRAIN: ASSAY, SOME PROPERTIES, AND DISTRIBUTION 1

Abstract— Arylsulphatases (aryl‐sulphate sulphohydrolases; E.C. 3.1.6.1) in human brain were studied using a highly sensitive fluorometric technique based on the use of 4‐methyl‐umbelliferone sulphate (MUS) as substrate. In the dialysed homogenate of human brain at least two enzymes could be distinguished on the basis of pH optima and substrate concentration. One MUS‐sulphatase, of the ‘insoluble’ type, exhibited a pH optimum of 6–9 and an apparent Km of 0.05 mM, whereas the second, belonging to the ‘soluble’ type, exhibited pH optimum of 6–0 and an apparent Km of 6.25 mM. Pronounced activities of the two arylsulphatases were observed in the 18,000 g sediment. About 25 per cent of the total tissue activity of the ‘soluble’‐type MUS‐sulphatase was found in the soluble subcellular fraction. However, this enzyme was completely solubilized by extraction of acetone‐dried human brain with acetate buffer.