The iduronate sulphatase activities of cells and tissue fluids from patients with Hunter syndrome and normal controls.

The substrate O-(alpha-L-idopyranosyluronic acid-2-sulphate)-(1 leads to 4)-2,5-anhydro-D-(3H-1) mannitol-6-sulphate was used at a final concentration of 50 mmol/l to measure the alpha-L-idurono-2-sulphate sulphatase activities of cell extracts, serum and amniotic fluid. Activities were measured after dialysis against water, to avoid the inhibitory effect of sodium chloride and the reaction products separated by ion-exchange chromatography on ECTEOLA cellulose. The enzyme present in normal serum had an apparent Km of 0.12 mmol/l. The mean activities of normal serum, fibroblasts and leukocytes were 0.61, 16.63 and 18.75 nmol/mg protein per hour respectively, while corresponding 'Hunter' tissues contained between 1% and 3% of normal activity. Cultured normal amniotic cells had a mean activity of 8.46 nmol/mg protein per hour, while those cultured from 'Hunter' patients contained about 6% of normal activity. Hunter disease can thus be readily diagnosed in a wide variety of tissues. Samples from three obligate heterozygotes were found to have iduronate sulphatase activities amounting to 41%, 57% and 63% of normal values.