A substrate for direct measurement of L-iduronic acid 2-sulfate sulfatase.

Commercially available sodium heparinate has been sequentially treated with methanolic 0.06M hydrogen chloride and nitrous acid. The nondegraded material was separated by gel filtration from the nonsulfated and monosulfated disaccharides produced. The latter ones, obtained in 10% yield, have been used as a substrate for the direct measurement of the enzyme L-iduronic acid 2-sulfate sulfatase present in human plasma and fibroblast homogenates. Studies of the kinetics and pH optimum of the enzyme, by use of plasma of a patient with mucolipidosis II, indicated an apparent Km of 2.5mM and a pH optimum of 4.6--4.8. The levels of activity in normal plasma and plasma of a patient with Hunter's disease were found to be 20.4 +/- 1.22 units (mumol sulfate/24 h/g protein) and 3.25 +/- 0.35 units, respectively. In homogenates of cultured skin fibroblasts, the levels were 137.6 +/- 10.7 units for normal controls and 6.4 +/- 5.1 for patients with Hunter's disease. The plasma two obligated heterozygotes gave intermediate levels of activity, whereas the plasma of two possible heterozygotes gave either intermediate levels or entirely normal levels of activity.