The activation of an arylsulphatase from ox liver by chloride and other anions

Abstract

The partial purifi-cation of an enzyme in ox liver hydrolyzing p-nitrophenylsulfate (NPS) and 2-hydroxy-5-nitrophenyl sulfate (NCS) is described. The use of the Ratio Recording Spectrophotometer for following the progress of NPS hydrolysis is described. The hydrolysis of NPS by the enzyme is strongly activated by Cl- and some other univalent anions whereas the hydrolysis of NCS by the enzyme is inhibited by Cl-. The apparent affinities for activating anions, as observed by NPS hydrolysis, increase in the order Cl-, Br-, NO3-, ClO3-, I-, SCN-. The maximum velocity obtained with each ion except ClO3- is almost the same; but the velocity falls off at higher concentrations of thiocyanate, NO3[long dash]and I-. The activity of the enzyme towards NPS in the absence of added salts could not be reduced below 9% of that in 0.17 [image]-NaCl. Chloride has little effect on the dependence of either NPS or NCS hydrolysis on pH, and has no effect on the affinity of the enzyme for either NPS or NCS. Phosphate, SO4[long dash]and F" inhibit the action of the enzyme on both NPS and NCS; the effect is not due to competition with activator, but PO4[long dash]- and SO4[long dash]may compete with substrate. Mixed-substrate experiments suggest that both substrates are attacked by a single enzyme in the preparation. The implications of this work for the characterization of sulfatases and the relationship of the present enzyme to the arylsulfatases previously described are discussed.