Abstract: The acid phosphatase (E.C.3.1.3.2) was purified from Apostichopus japonicus by following procedures: ammonium sulfate fraction precipitation,ammonium sulfate precipitation and gelfiltraction chrcmatography on Sephadex G-200. The purified acid phosphatase shows a single electrophoretic band on PAGE pattern. The enzyme has a maximum absorption peak at 220 nm and 280 nm respectively and its fluorescence emission wavelength is 300 nm and its fluorescence excitation wavelengths are 306.3 nm and 606.3 nm. The isoelectric point is 4.2. The optimum pH of the acid phosphatase is 4.4 when pNPP is used as substrate and the optimum temperature is 45 ℃. The initial velocity is 0.2591μmol/min and the Michaelis-Menten kinetics (Km) is 0.816 ×10-4 mol/L. The heavy metal ions,such as Hg2+,Ag+,Cd2+ and Pb2+ inhibit the activity of the enzyme obviously,and the order is: Hg2+>Ag+>Pb2+>Cd2+.

Key words: Apostichopus japonicu, sacid phosphatase, separation and purification, characterization