Purification of acid phosphatase I from germinating seeds of Vigna sinensis.

Acid phosphatase I (AP-I) is the major isoform of Vigna acid phosphatase. It is constitutively expressed in seed cotyledons during germination. AP-I was separated from other isoforms and purified to homogeneity by three simple purification steps; (NH4)2SO4 precipitation, and phosphocellulose and DEAE-cellulose column chromatography. The activity of AP-I was not affected by 1 mM Mg2+, Mn2+, Ca2+, Co2+ or Pb2+, but severely inhibited by 1 mM Cu2+, Fe3+, Hg2+, Mo6+ or Zn2+. AP-I has both phosphatase and pyrophosphatase activities, and is highly stable even at 50 degrees.