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.


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.

Publication types

  • Comparative Study

MeSH terms

  • Chondroitinases and Chondroitin Lyases / analysis*
  • Chondroitinsulfatases / analysis*
  • Clinical Enzyme Tests
  • Fibroblasts / enzymology
  • Fluorescent Dyes
  • Fluorometry
  • Humans
  • Hydrogen-Ion Concentration
  • Leukocytes / enzymology
  • Mucopolysaccharidosis IV / diagnosis*


  • Fluorescent Dyes
  • Chondroitinsulfatases
  • Chondroitinases and Chondroitin Lyases