A fluorimetric enzyme assay for the diagnosis of MPS II (Hunter disease).
4-Methylumbelliferyl-alpha-iduronate 2-sulphate was synthesized and shown to be a specific substrate for the lysosomal iduronate-2-sulphate sulphatase (IDS). Fibroblasts (n = 17), leukocytes (n = 3) and plasmas (n = 9) from different MPS II patients showed < 5% of mean normal IDS activity. The enzymatic liberation of the fluorochrome from 4-methylumbelliferyl-alpha-iduronate 2-sulphate requires the sequential action of IDS and alpha-iduronidase. A normal level of alpha-iduronidase activity was insufficient to complete the hydrolysis of the reaction intermediate 4-methylumbelliferyl-alpha-iduronide formed by IDS. A second incubation step in the presence of excess purified alpha-iduronidase is needed to avoid underestimation of the IDS activity.
Voznyi
Y V
YV
Institute of Organic Chemistry, Moscow, Russia.
Keulemans
J L
JL
van Diggelen
O P
OP
D005347:Fibroblasts / Q000201:enzymology; D005470:Fluorometry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D007066:Iduronate Sulfatase / Q000097:blood / Q000378:metabolism; D007067:Iduronic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D007962:Leukocytes / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D016532:Mucopolysaccharidosis II / Q000175:diagnosis* / Q000201:enzymology*; D013379:Substrate Specificity
C456019:4-methylumbelliferyliduronate 2-sulfate; D007067:Iduronic Acid; D006923:Hymecromone; D007066:Iduronate Sulfatase