The kinetic parameters (Km and V) of human
arylsulphatase B (4-sulpho-N-acetylgalactosamine sulphatase) activity in cultured skin fibroblasts were determined with a variety of substrates matching structural aspects of the physiological substrates in vivo
chondroitin 4-sulphate and dermatan sulphate. More structurally complex substrates, in which several aspects of the aglycone structure of the natural substrate were maintained, were desulphated up to 4400 times faster than the minimum
arylsulphatase-B-specific substrate, namely the
monosaccharide N-
acetylgalactosamine 4-sulphate. Aglycone structures that influence substrate binding and/or
enzyme activity were an adjacent-residue C-6 carboxy group and a second but internal N-
acetylgalactosamine 4-sulphate residue.
Arylsulphatase B activity in fibroblast homogenates assayed with O-(beta-N-
acetylgalactosamine 4-sulphate)-(1----4)-O-D-(beta-
glucuronic acid)-(1----3)-O-D-N-acetyl[1-3H]
galactosaminitol 4-sulphate derived from
chondroitin 4-sulphate as substrate clearly distinguished
Maroteaux-Lamy-syndrome patients from normal controls and other
mucopolysaccharidosis patients. We recommend the use of the above
trisaccharide substrate for both postnatal and prenatal diagnosis of
Maroteaux-Lamy syndrome.