Reduced C₂₇-steroid 26-hydroxylase activity in heterozygotes for cerebrotendinous xanthomatosis

Steinar Skrede Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway

I. Björkhem Department of Clinical Chemistry and Research Center at Huddinge, University Hospital, Karolinska Institutet, Stockholm, Sweden

E. A. Kvittingen Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway

C. East Center for Human Nutrition, Department of Internal Medicine, Dallas, Texas

S. Grundy Center for Human Nutrition, Department of Internal Medicine, Dallas, Texas

Sverre Skrede Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway

Abstract

C₂7-steroid 26-hydroxylase activity in fibroblasts from two heterozygotes for CTX was determined, using an optimized enzyme assay. With 5β-cholestane-3α, 7α, 12α-triol, 5β-cholestane-3α, 7α-diol, 7α-hydroxy-4-cholesten-3-one or 7α-hydroxycholesterol as substrates, the activities were about 50% of those of control cells. The K_m 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.

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Reduced C₂₇-steroid 26-hydroxylase activity in heterozygotes for cerebrotendinous xanthomatosis

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Reduced C27-steroid 26-hydroxylase activity in heterozygotes for cerebrotendinous xanthomatosis

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Reduced C₂₇-steroid 26-hydroxylase activity in heterozygotes for cerebrotendinous xanthomatosis