Steroid sulphatase in man: A non inactivated X-locus with partial gene dosage compensation

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Abstract
Steroid sulphatase (STS) activity was measured with two different steroid substrates in leucocytes from normal human males and females, from females heterozygous for STS deficiency and recessive X-linked ichthyosis, and from individuals with numerical X chromosome aberrations. The results indicate non-inactivation with a partial gene dosage compensation at the STS locus. It is estimated that STS loci on inactive X chromosomes express approximately 45% of the STS activity originating from STS loci on active X chromosomes. It is also demonstrated that 45.XO (Turner syndrome) and 47,XXY (Klinefelter syndrome) individuals have abnormal STS enzyme levels compared with normal women and men, respectively.