Abstract:

Electrophoresis-pure acid phosphatase (ACP) was obtained from sweet potato old leaves via a series of
consecutive procedures, including homogenization, extraction, ammonium sulfate fractional precipitation, DEAEsepharose
chromatography and Superdex-200 gel filtration and then identified with sodium dodecyl sulfate polyacrylamide
gel electrophoresis (SDS-PAGE). In this process, the purification fold was 169.07 and the recovery of ACP activity was
3.50%. The specific activity of the purified enzyme was 251.49 U/mg. The result showed that the enzyme was a single
subunit protease with a relative molecular weight of 42.3 kD, and the subunit molecular weight was 41.2 kD. The optimum
temperature and pH of the ACP enzyme were 65 ℃ and 5.2, respectively. This ACP was stable below 40 ℃ and in the pH
range from 4.0 to 6.0. Its Michaelis-Menten Kinetics (Km) towards p-nitrophenyl phosphate was 0.258 mmol/L. The enzyme
activity could be obviously inhibited by methanol, EDTA and oxalic acid and also strongly inhibited by Hg2+ and Ag+.

Key words: sweet potato leaves, acid phosphatase, isolation and purification, characterization