The association of X-linked ichthyosis with a deficiency of steroidsulfatase was demonstrated biochemically in cultured skin fibroblasts and epidermal cells in recent years [9,2]. A simultaneous deficiency of arylsulfatase C in this inborn error was shown histochemically in skin sections by Koppe et al. [1] and biochemicaUy in cultured skin fibroblasts by Meyer et al. [3]. Since it takes rather a long time to cultivate enough skin fibroblasts for the sulfatase assay it was obvious to look for a simpler and faster biochemical method. A first attempt was the estimation of arylsulfatase C activity in hair follicles [4], a method which is often used for the detection of heterozygotes in X-linked inherited enzyme disorders [5]. A certain trend to lower arylsulfatase C levels in hair follicles as reported in this communication [4] could not be confirmed, even when we used ~-galactosidase as reference enzyme to rule out different hair qualities. In a second trial towards a faster biochemical determination of XLI, we started to estimate arylsutfatase C activity in skin preparations. Because arylsulfatase C is an insoluble microsomal enzyme [6], we prepared a membranous fraction from skin biopsies to avoid a contamination of the two soluble lysosomal arylsulfatases A and B as described below. For technical reasons, the simultaneous demonstration of steroid-sulfatase and arylsulfatase in skin preparations of XLI and ADI was not possible.
The crude skin biopsies were trimmed free of fat, cut into small pieces, and four times forced through a freeze press (X-Press, LKB Produkteur AB, Bromma, Sweden) in a 1 ml solution of 1 mg/ml bovine serum albumin (BSA). The resulting homogenate was suspended in 20 ml BSA solution and further homogenized in a Polytron homogenizer (Kinematica GmbH, Kriens, Switzerland) and finally sonicated 5 min with a sonication tip (Heat Systems Ultrasonics, Inc., 38 East Mall, Plain View, L.I., NY 11803, USA). This crude homogenate was centrifuged for 2 h at 50,000 β’ g at 4 ~ C in a refrigerated Sorvall RC-5 centrifuge (Dupont Company, Instrument Products, Biomedical Div., Newtown, CT 06570, USA). The pellet was again suspended in 20 ml BSA solution and treated with the Polytron homogenizer, sonicated, and centrifuged as mentioned above. The resulting sediment was freezedried and then stored at -20 ~ C. For the estimation of arylsulfatase C activity 1.5mg dry weight of freeze-dried material were suspended in 50gl of 0.2M