Aryl sulfatase from Naja nigricolis venom: characterization and possible contribution in the pathology of snake poisoning

The venom of Naja nigricolis was found to contain a high level of the enzyme aryl sulfatase. The enzyme was isolated from the venom of N. nigriclois and purified to electrophoretic homogeneity by gel chromatography on Sephadex G-100, DEAE-cellulose, and phenyl-sepharose columns. The enzyme was optimally active at pH 5 and 40 degrees C. Arrhenius plot for the determination of the activation energy (E(a)) gave the value 25 kJ/mol with a half-life (t(1/2)) of 5 min at 50 degrees C. It was highly activated by Fe(2+) and Ca(2+) and inhibited by Co(2+) and Mn(2+). The enzyme catalyzed the hydrolysis of the fluorescent compound methylumbelliferyl-sulfate (MU-SO(4)). Double reciprocal plots of initial velocity data, using MU-SO(4) as substrate, gave a K(M) value of 110 microM and V(max) of 225 micromol min(-1) x mg(-1). N. nigricolis Aryl sulphatase also hydrolyzed chondroitin-4-sulphate. It was inhibited competitively by N-acetyl glucosamine sulfate (GlcNAc-SO(4)), glucose-6-sulfate (Glc-6-SO(4)), and glucose 1-sulfate (Glc-1-SO(4)). Extrapolated inhibition binding constants (K(i)) gave the values of 3, 25, and 315 microM for GlcNAc-SO(4), Glc-6-SO(4), and Glc-1-SO(4) respectively.