Abstract:

Electrophoresis-purity tyrosinase (TYR) from Ipomoea Aquatica Forsk leaves was obtained through
homogenization, buffer solution extraction, ammonium sulfate precipitation, DEAE-Sepharose ion exchange chromatography
and Superdex-200 gel filtration chromatography. The specific activity of purified TYR was 114.53 U/mg, with a recovery
of 11.33% and a purification factor of 99.59. The molecular weights of TYR and its subunit were 77.60 kD and 38.70 kD,
respectively. TYR was relatively stable in the range of 25–55 ℃ and pH 6.0–8.0. Its optimum temperature and pH were
45 ℃ and 7.5, respectively. Furthermore, its Km was 10.05 mmol/L under the optimum conditions. The activity of TYR could
be inhibited by methanol, ethanol, isopropanol and citric acid and ascorbic acid, as well as some metal ions such as Ca2+and
Pb2+. It could be activated by Mn2+, Zn2+ and Co2+; however, urea and SDS had little effect on its activity, and Li+ and K+ has
no effect on its activity.

Key words: Ipomoea aquatica Forsk. leaves, tyrosinase, isolation and purification, characterization