Reduced C27-steroid 26-hydroxylase activity in heterozygotes for cerebrotendinous xanthomatosis.
C27-steroid 26-hydroxylase activity in fibroblasts from two heterozygotes for CTX was determined, using an optimized enzyme assay. With 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol, 5 beta-cholestane-3 alpha,7 alpha-diol, 7 alpha-hydroxy-4-cholestane-3-one or 7 alpha-hydroxycholesterol as substrates, the activities were about 50% of those of control cells. The Km for the substrates was not increased in the CTX heterozygotes. These findings support that deficiency of the C27-steroid 26-hydroxylase is the primary enzymatic defect in CTX.
Skrede
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Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway.
Björkhem
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I
Kvittingen
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EA
East
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C
Grundy
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Skrede
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D000328:Adult; D001927:Brain Diseases / Q000201:enzymology* / Q000235:genetics; D002478:Cells, Cultured; D005260:Female; D006579:Heterozygote; D006801:Humans; D008297:Male; D013710:Tendons; D014973:Xanthomatosis / Q000201:enzymology* / Q000235:genetics