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

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.