Isolation and partial characterization of an acid phosphatase from Artemisia vulgaris pollen extract

Abstract

An acid phosphatase from an extract of mugwort (Artemisia vulgaris) pollen was purified by a factor of 48 by a combination of ion exchange and gel-chromatography. The molecular weights of the enzyme were 76 kDa and 73 kDa, determined by gel filtration on a Sephadex G-100 sf column and by SDS PAGE(under reducing and non-reducing conditions), respectively. In analytical isoelectrofocusing, the enzyme appears as two very close bands pI at about 4.2. The optimum pH for the enzyme is 5.4. The apparent Km for p-nitrophenyl phosphate was estimated to be 0.16mM. The purified enzyme has broad specificity, and hydrolyses p-nitrophenyl phosphate and ?-naphthyl phosphate. Pyrophosphate and O-phospho-L-tyrosine were estimated to be the best substrates for this enzyme as potential in vivo substrates. The enzyme is inhibited competitively by phosphate (Ki = 1.25 mM), molybdate (Ki = 0.055 mM) and pyrophosphate (Ki = 6.7 mM) and non-competitively by fluoride (Ki = 9.8 mM). Metal ions such as Hg2+, Cu2+ and Zn2+ express an inhibitory effect on the enzyme, while the enzyme is slightly activated by non-ionic detergents, Tween 20 and Triton X-100. There is no change in the enzyme activity in the presence of tartrate, citrate, EDTA, 1,10-phenanthroline and sulfhydryl-group modifiers such as p-chloromercuribenzoate and N-ethylmaleimide.