Morquio A syndrome (MPS IVA) results from a deficiency of the N-acetylgalactosamine-6-sulfate sulfatase enzyme. This enzyme hydrolyzes a sulfate group from the 6 position of galactose at the nonreducing terminus of the mucopolysaccharides, keratin sulfate and chondroitin-6 sulfate. In this procedure, 4MU-beta-D-galactoside-6-sulfate is used as the substrate. The enzyme will cleave the 6-sulfate from the galactose residue and a second incubation with excess beta-galactosidase will cleave the 4MU which is measured fluorometrically and calculated against a calibration of 4MU.(Package insert: Laboratory protocol for enzyme analysis for Morquio A disease [MPS IV A]. Moscerdam Substrates, The Netherlands; van Diggelen OP, Zhao H, Kleijer WJ, et al: A fluorimetric enzyme assay for the diagnosis of Morquio disease type A. Clin Chim Acta 1990;187:131-140)
WBC homogenate stored 1 month.