Biochemical characterization of arylsulfatase-C isozymes in human fibroblasts

• Published in: Biochemical and biophysical research communications Vol. 128; no. 3; pp. 1388 - 1394
• Main Authors: Simard, Jean-Pierre S., Ameen, Mohammed, Chang, Patricia L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 16.05.1985
• Subjects: Arylsulfatases - immunology; Arylsulfatases - metabolism; arylsulphatase; Cells, Cultured; Cross Reactions; fibroblasts; Fibroblasts - enzymology; Hot Temperature; Humans; Hydrogen-Ion Concentration; Ichthyosis - enzymology; Isoenzymes - immunology; Isoenzymes - metabolism; Kinetics; man; Steryl-Sulfatase; Sulfatases - metabolism
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(85)91094-0

Arylsulfatase-C and sterol sulfatase were thought to be identical enzymes whose X-linked locus escapes inactivation. However, recent evidence shows that they are not identical but that arylsulfatase-C in human fibroblasts exists in two isozymic forms, designated as slow and fast . We now report that the two forms are enzymatically different. When assayed with an artificial fluorogenic substrate, the slow form showed a pH optimum of 8.00 and a Km of 228 μM. In contrast, the fast form showed a pH optimum of 7.67 and a Km of 86.7 μM with substrate inhibition occurring above 0.33 mM. The heat stability of the fast form was slightly below that of the slow form. Polyclonal antibodies raised against the slow form did not cross-react with the fast form. Hence, the two isozymic forms of arylsulfatase-C are enzymatically and structurally different and the slow form is associated with sterol sulfatase activity.