Effect of CuCl 2, NaCl and EDTA on the enzyme α- l-iduronidase in the plasma of normal individuals and heterozygotes for MPS I

Abstract

Background: It has been previously demonstrated that the enzyme α- l-iduronidase (IDUA) of patients with MPS I shows a different biochemical behavior in each of the three clinical forms of these. In heterozygotes, its biochemical behavior has been recently established in leukocyte and plasma samples, demonstrating that it is possible to distinguish individuals heterozygous for MPS I within an unselected population. Methods: We evaluated the effect of copper chloride, EDTA and sodium chloride on the activity of the enzyme α- l-iduronidase in the plasma of normal individuals and of MPS I heterozygotes and observed the type of inhibition caused, the Ki, the apparent Km and the apparent Vmax for each inhibitor. Results: Sodium chloride inhibited the enzyme in normal individuals and in 40% of the heterozygotes evaluated and activated it in 60% of heterozygotes. The remaining compounds inhibited IDUA in both heterozygotes and normal individuals. Conclusions: We detected significant differences capable of differentiating MPS I heterozygotes from normal individuals by simply adding sodium chloride, EDTA or copper chloride to the incubation medium at the time of IDUA activity determination, with a potential use in carrier detection protocols.