title: A fluorimetric enzyme assay for the diagnosis of Morquio disease type A (MPS IV A).
abstract: 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.
authors.affiliation: Department of Clinical Genetics, University Hospital, Erasmus University, Rotterdam, The Netherlands.
authors.forename: O P
authors.initials: OP
authors.lastname: van Diggelen
authors.forename: H
authors.initials: H
authors.lastname: Zhao
authors.forename: W J
authors.initials: WJ
authors.lastname: Kleijer
authors.forename: H C
authors.initials: HC
authors.lastname: Janse
authors.forename: B J
authors.initials: BJ
authors.lastname: Poorthuis
authors.forename: J
authors.initials: J
authors.lastname: van Pelt
authors.forename: J P
authors.initials: JP
authors.lastname: Kamerling
authors.forename: H
authors.initials: H
authors.lastname: Galjaard
mesh_terms: 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*
chemical_list: D005456:Fluorescent Dyes; D002811:Chondroitinsulfatases; D002810:Chondroitinases and Chondroitin Lyases