Detailed studies on the hydrolysis of p-acetylphenyl sulphate and oestrone sulphate by rat liver preparations strongly indicate that arylsulphatase C and oestrogen sulphatase are the same enzyme. Liver is the richest source of both enzymes, which have identical intracellular distributions, being localized mainly in the microsomal fraction. Low oestrogen sulphatase and arylsulphatase C activities were present in foetal liver and these increased at a similar rate after birth. The activities of the enzymes in an ethionine-induced hepatoma were similarly low. Results of heat inactivation, mixed-substrate and competitive-inhibition experiments employing liver microsomal fractions were also consistent with one enzyme being involved. Oestradiol-17β 3-sulphate was also hydrolysed by microsomal preparations and activity towards both this substrate and oestrone sulphate was inhibited by oestrone and oestradiol-17β. The physiological significance of this inhibition is discussed.
