Enzymatic diagnosis of Morquio A syndrome with a new fluorimetric substrate.

We synthesized a new fluorimetric substrate for the enzymatic assay of galactose 6-sulphate sulphatase (Gal-6S), an enzyme which is deficient in Morquio A syndrome. Our synthetic 4-methylumbelliferyl-galactoside 6-sulphate (4Mu-Gal-6S) proved highly effective and sensitive in the postnatal, prenatal and retrospective diagnosis of Morquio A syndrome as compared to the commonly used radiolabelled substrate. With 4Mu-Gal-6S as substrate and dialyzed supernatant as the enzyme source, we defined the optimal assay conditions for Gal-6S, determined the normal control values for all available materials, and successfully performed postnatal and prenatal diagnosis of Morquio A syndrome.