Regulation of arylsulphatases: inhibition of arylsulphatase from Haliotis rufusensis by phosphoric esters and shift of optimal pH depending on temperature

Arylsulphatase activity of Haliotis rufusensis has been tested at different temperatures and pH. This enzyme is characterized by an optimum temperature at +50°C. The maximum pH activity is depending on temperature; by increasing temperature from +20 to + 50°C, a shift of pH maximum has been observed towards the acidic side. The enzyme activity was tested with nitrocatecholsulphate, synthetic substrato, and with natural substrates, cerebroside sulphate and ascorbate 2-sulphate. These naturai substrates are "competitive" with respect to thè synthetic substrate. Nitrophenylphosphate is a powerful inhibitor of this enzyme; this effect is pH dependent. Several phosphoderivatives, including inositol-phosphatides and myo-inositolphosphate, are also important inhibitors. Arylsulphatase from Haliotis, like those from Heìix and Palella, is a glycoprotein (muramyl-glycoprotein). Its electrophoretic behaviour is similar to that of arylsulphatase A from human liver, but AgNÒ3 or NaCl treatment are ineffective in differentiating A and B forms.