Assays / Genetic Enzymes / Steroid Sulphatase and Arylsulphatase C

PRINCIPLE OF METHODS: Steroid sulphatase is assayed using [3H]-dehydroepiandrosterone sulphate as substrate, the de-sulphated product being separated by solvent partitioning. Arylsulphatase C, which is probably identical to steroid sulphatase, is assayed using a methylumbelliferyl derivative as substrate and measuring fluorescence of the released 4-methylumbelliferone. It is the practice of the lab to assay both enzymes simultaneously on all test specimens.

USES AND LIMITATIONS OF THE METHODS: The enzyme is deficient in X-linked ichthyosis. The assay is carried out to confirm this type of ichthyosis, and distinguish it from others that have various patterns of inheritance or which may be sporadic. In the fetus the enzyme deficiency leads to diminished oestrogen biosynthesis, often leading to prolonged labour. Prenatal diagnosis should be possible by measuring the enzyme in chorionic villi, but is not offered by the SAS laboratory. The enzyme is also deficient in multiple sulphatase deficiency, being the only non-lysosomal sulphatase that is defective in this disease. Steroid sulphatase is also deficient in the contiguous gene syndrome, which involves deletion of several disease genes located in the Xp22.3 region.

SPECIMEN REQUIREMENTS: Fibroblasts cultured from a skin biopsy are needed. Biopsy material should be collected aseptically into a sterile bottle containing tissue culture medium (available from the laboratory), and sent at room temperature to arrive at the laboratory [hyperlink to main page] within 24 hours. Biopsies for tissue culture should not be frozen. Fibroblast cultures established in other laboratories should be sent in plastic 25 cm2 flasks filled with medium.

THE LABORATORY RECOMMENDS USE OF A COURIER SERVICE OR ROYAL MAIL SPECIAL DELIVERY FOR SENDING ALL SPECIMENS TO THE LABORATORY

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