Substrate specificity of alpha-glucuronidase isolated from snail acetone powder

The substrate specificity of a p-nitrophenyl alpha-D-glucopyranosyl-uronic acid-hydrolyzing enzyme (PNP-GAase) isolated from snail acetone powder has been investigated with various substrates, such as p-nitrophenyl alpha-D-glucopyranosyluronic acid (PNP-GA), 2-O-alpha- D-glucopyranosyluronic acid-D-xylose (GA-2X), 2-O-(4-O-methyl-alpha-D-glucopyranosyluronic acid)-D-xylose (MeGA-2X), and O-alpha-D-glucopyranosyluronic acid-alpha-D-glucopyranosiduronic acid (GA-GA). The Km (mM) and Vmax (mumol of glucuronic acid formed/mg of enzyme protein/min) toward these substrates were as follows; 0.13 and 3.21 for PNP-GA, 0.33 and 0.089 for GA-2X, 17.6 and 0.094 for MeGA-2X, and 0.36 and 0.015 for GA-GA, respectively. The results indicate that the PNP-GAase specifically hydrolyzed PNP-GA, however, the enzyme had broad substrate specificity.