Fluorometric Measurement of ƒ ¿ - L - Iduronidase Activity Using 4 - Methylumbelliferyl - - L - Iduronide

ylumbelliferyl-ƒ¿-L-iduronide as a substrate, ƒ¿-L-iduronidase activity was meas ured in leukocytes and in lymphoblastoid cells obtained from patients with ƒ¿-L-iduronidase deficiency and from obligate heterozygotes for this disease . There was complete discrimination between ƒ¿-L-iduronidase activities measured using 4-methylumbelliferyl-ƒ¿-L-iduronide in leukocytes and in lymphoblastoid cells from the patients and controls. However, overlap was observed between values of the activity in the obligate heterozygotes and those in the controls. 4-Methylumbelliferyl-ƒ¿-L-iduronide is superior to phenyl-ƒ¿-L-iduronide for the determination of ƒ¿-L-iduronidase activity because of greater sensitivity, easier assay procedure and shorter incubation period. ƒ¿-L-iduronidase; 4methylumbelliferyl-ƒ¿-L-iduronide; Hurler and Scheie syndromes