ABSTRACT
Nucleotides and calcium ions have been implicated in the regulation of biosynthesis of steroids, although the exact locus of calcium activity is not yet known. The administration of Ca2+ to Leydig cells increases testosterone production. Steroid sulfatase activity is reported to be enhanced by adenine nucleotides. In the present study the testicular sulfatase was evaluated in subcellular fractions by conversion of sulfate to free steroids in the presence or absence of Ca2+ and Mg2+ ions. The specific activity of the enzyme, which was located predominantly in submitochondrial fraction, showed a positive correlation with calcium, increasing 1.5-fold in the presence of 2.54 mM of calcium (62 nmol/h mg protein-1). In contrast, magnesium inhibited the enzymatic activity 1.79-fold in presence of 1.18 mM (23 nmoles/h mg protein-1). It would appear that testicular sulfatase is predominantly located in the mitochondria, which is recognized as one of the major sites of control of intracellular metabolism, and that its enzymatic activity could be modulated by calcium regulating the levels of potentially active androgens.
