BIOCHEMICAL-CHARACTERIZATION OF ARYLSULFATASE-E AND FUNCTIONAL-ANALYSIS OF MUTATIONS FOUND IN PATIENTS WITH X-LINKED CHONDRODYSPLASIA PUNCTATA

X-linked chondrodysplasia punctata (CDPX) is a congenital disorder cha racterized by abnormalities in cartilage and bone development. Mutatio ns leading to amino acid substitutions were identified recently in CDP X patients, in the coding region of the arylsulfatase E (ARSE) gene, a novel member of the sulfatase gene family, Transfection of the ARSE f ull-length cDNA, in Cos7 cells, allow ed us to establish that its prot ein product is a 60-kD precursor, which is subject to N-glycosylation, to give a mature 68-kD form that, unique among sulfatases, is localiz ed to the Golgi apparatus. Five missense mutations found in CDPX patie nts were introduced into wild-tyre ARSE cDNA by site-directed mutagene sis. These mutants were transfected into Cos7 cells, and the arylsulfa tase activity and biochemical properties were determined, to study the effect of thee substitutions on the ARSE protein, One of the mutants behaves as the wild-type protein. All four of the other mutations resu lted in a complete lack of arylsulfatase activity, although the substi tutions do nor appear to affect the stability and subcellular localiza tion of tile protein. The loss of activity due to these mutations conf irms their involvement in the clinical phenotype and paints to the imp ortance of these residues in the correct folding of a catalytically ac tive ARSE enzyme.