A fluorimetric enzyme assay for the diagnosis of Morquio disease type A (MPS IV A)

  • Clin Chim Acta. 1990 Feb 28;187(2):131-9. doi: 10.1016/0009-8981(90)90339-t.
O P van Diggelen  1 ,  H Zhao ,  W J Kleijer ,  H C Janse ,  B J Poorthuis ,  J van Pelt ,  J P Kamerling ,  H Galjaard
Affiliations
  • 1. Department of Clinical Genetics, University Hospital, Erasmus University, Rotterdam, The Netherlands.
PMID: 2107987 DOI: 10.1016/0009-8981(90)90339-t
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.

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