A fluorimetric enzyme assay for the diagnosis of Sanfilippo disease type D (MPS IIID).
4-Methylumbelliferyl-alpha-N-acetylglucosamine 6-sulphate was synthesized and shown to be a substrate for the lysosomal N-acetylglucosamine-6-sulphate sulphatase (GlcNAc-6S sulphatase). Fibroblasts and leukocytes from 3 different Sanfilippo D patients showed < 1% of mean normal GlcNAc-6S sulphatase activity. The enzymatic liberation of the fluorochrome from 4-methyl-umbelliferyl-alpha-N-acetylglucosamine 6-sulphate requires the sequential action of the GlcNAc-6S sulphatase and alpha-N-acetylglucosaminidase. A normal level of alpha-N-acetylglucosaminidase activity was insufficient to complete the hydrolysis of the reaction intermediate 4-methylumbelliferyl-alpha-N-acetylglucosaminide formed by the GlcNAc-6S sulphatase. A second incubation in the presence of excess alpha-N-acetylglucosaminidase is needed to avoid underestimation of the GlcNAc-6S sulphatase activity.
He
W
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Department of Clinical Genetics, Erasmus University, Rotterdam, The Netherlands.
Voznyi YaV
Boer
A M
AM
Kleijer
W J
WJ
van Diggelen
O P
OP
D000117:Acetylglucosamine / Q000031:analogs & derivatives; D005347:Fibroblasts / Q000201:enzymology; D005470:Fluorometry; D006801:Humans; D006923:Hymecromone / Q000031:analogs & derivatives; D007962:Leukocytes / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D009084:Mucopolysaccharidosis III / Q000175:diagnosis* / Q000201:enzymology*; D009942:Organometallic Compounds / Q000494:pharmacology; D013379:Substrate Specificity; D013429:Sulfatases / Q000032:analysis*
D009942:Organometallic Compounds; C025158:4-methylumbelliferyl 2-acetamido-2-deoxy-beta-D-glucopyranoside; D006923:Hymecromone; D013429:Sulfatases; C018719:N-acetylglucosamine-6-sulfatase; C008261:lead acetate; D000117:Acetylglucosamine