Studies on oestrone sulphate sulphohydrolase from human placenta nuclear envelopes--solubilization and properties

Kinetic properties of human placenta nuclear envelope oestrone sulphate sulphohydrolase were determined in envelope suspension, Triton X-100 solubilized enzyme preparations and in partially purified enzyme preparations. Purification of the enzyme(s) extracted with Triton X-100 was performed by three alternative procedures: Bio-gel A 15 m chromatography, DEAE-cellulose chromatography and Con-A-Sepharose chromatography. The nuclear envelope suspension revealed optimal hydrolysis of oestrone sulphate at pH 8.2; the Triton X-100 solubilized enzyme exhibited optimal activities at pH 6.6 and 8.6. Three distinct activity peaks of oestrone sulphate hydrolysis were found for the partially purified enzyme preparations: at pH 6.2 (5.8-6.6), at pH 7.0 and pH 8.4 (8.0-8.8). The influence of the oestrone sulphate concentration on the enzyme activity determined at pH 6.2 exhibited a sigmoid saturation kinetics with all enzyme preparations except that obtained after Con-A Sepharose chromatography. The value of Hill (h) coefficient was 2; S0.5 = 65 microM, the K'm = 4.9 x 10(-9) M. At pH 7.0 and 8.4, the influence of oestrone sulphate concentration on enzyme activity revealed a Michaelis-Menten saturation kinetics; the respective values of Km were 4.2 +/- 1.1 x 10(-6) M and 1.08 +/- 0.11 x 10(-4) M. The Km value of oestrone sulphate hydrolysis of the enzyme preparation after Con-A Sepharose chromatography determined at pH 6.2, 7.0 or 8.1 was 4.0 x 10(-4) M.