Departments of Chemistry and Biochemistry, University

Mucopolysaccharidosis type I (MPS-I), caused by a defi-ciency of -l-iduronidase (IDUA; EC 3.2.1.76) activity, can manifest as three major phenotypes, usually defined by clinical criteria: Hurler (severe), Scheie (mild), and Hurl-er–Scheie (intermediate) syndromes. IDUA is crucial for degradation of glycosaminoglycans such as dermatan and heparan sulfate. Failure to break down these polysaccharides causes physical changes such as joint stiffness, skeletal abnormalities, and corneal clouding. Hurler syndrome is characterized by valvular heart disease, mental deterioration, and death in child-hood. Enzyme replacement therapy has been developed for MPS-I, and bone marrow transplantation is beneficial if performed early (1). Because early detection is neces-sary for optimum clinical response to therapy, the nee