A fluorimetric enzyme assay for the diagnosis of Morquio disease type A (MPS IV A).
4-Methylumbelliferyl-beta-D-galactopyranoside-6-sulphate was synthesized and used for the determination of galactose-6-sulphate sulphatase activity. Fibroblasts and leucocytes from 12 different Morquio A patients, showed 0.0-2.7% of mean normal galactose-6-sulphate sulphatase activity. Heterozygotes showed intermediate activities. The enzymatic liberation of the fluorochrome from 4-methylumbelliferyl-beta-D-galactopyranoside-6-sulphate requires the sequential action of galactose-6-sulphate sulphatase and beta-galactosidase. Normal beta-galactosidase activity caused nearly complete hydrolysis of non-fluorescing 4-methylumbelliferyl-galactoside, formed during incubation. In cell extracts with a beta-galactosidase deficiency however, a second incubation in the presence of excess beta-galactosidase is needed to avoid underestimation of galactose-6-sulphate sulphatase activity.
van Diggelen
O P
OP
Department of Clinical Genetics, University Hospital, Erasmus University, Rotterdam, The Netherlands.
Zhao
H
H
Kleijer
W J
WJ
Janse
H C
HC
Poorthuis
B J
BJ
van Pelt
J
J
Kamerling
J P
JP
Galjaard
H
H
D002810:Chondroitinases and Chondroitin Lyases / Q000032:analysis*; D002811:Chondroitinsulfatases / Q000032:analysis*; D004796:Clinical Enzyme Tests; D005347:Fibroblasts / Q000201:enzymology; D005456:Fluorescent Dyes; D005470:Fluorometry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007962:Leukocytes / Q000201:enzymology; D009085:Mucopolysaccharidosis IV / Q000175:diagnosis*
D005456:Fluorescent Dyes; D002811:Chondroitinsulfatases; D002810:Chondroitinases and Chondroitin Lyases