A fluorimetric enzyme assay for the diagnosis of Sanfilippo disease type A (MPS IIIA).
4-Methylumbelliferyl-alpha-D-N-sulphoglucosaminide (MU-alpha-GlcNS) was synthesized and shown to be a substrate for the lysosomal heparin sulphamidase. Sanfilippo A patients' fibroblasts (n = 42) and lymphocytes (n = 1) showed 0-3% of mean normal heparin sulphamidase activity; in total leukocytes from patients (n = 8) sulphamidase activity was clearly deficient. In fibroblasts from obligate heterozygotes for Sanfilippo A, the sulphamidase activity was reduced in 9 out of 10 cases. Heparin sulphamidase desulphates MU-alpha GlcNS to MU-alpha GlcNH2 and further hydrolysis during a second incubation is required to liberate 4-methylumbelliferone, which can be measured. Yeast alpha-glucosidase, which has low but sufficient alpha-glucosaminidase activity, was used to hydrolyse the reaction intermediate MU-alpha GlcNH2 to release 4-methylumbelliferone and free glucosamine.
Karpova
E A
EA
Department of Clinical Genetics, Erasmus University, Rotterdam, The Netherlands.
Voznyi YaV
Keulemans
J L
JL
Hoogeveen
A T
AT
Winchester
B
B
Tsvetkova
I V
IV
van Diggelen
O P
OP
D004796:Clinical Enzyme Tests; D005470:Fluorometry; D006801:Humans; D006867:Hydrolases / Q000378:metabolism; D009084:Mucopolysaccharidosis III / Q000175:diagnosis*
D006867:Hydrolases; C022708:N-sulfoglucosamine sulfohydrolase