Purification and characterization of secreted acid phosphatase in phosphorus-deficient Arabidopsis thaliana

Arabidopsis roots responded to the absence of an exogenous phosphate source with an increase in the specific activities of secreted acid phosphatases. Increases in enzyme activity were revealed beginning 2 days after P-withdrawal, reaching a maximum at 6 days. We characterized the secreted acid phosphatase. Two proteins, migrating at 52 and 63 kDa in SDS-PAGE, co-purified with the activity. Purified enzyme had a pH optimum of 5 and a pI of 5.9. In addition to the general phosphatase substrate, p -nitrophenyl-phosphate, the enzyme readily hydrolysed pyrophosphate, polyphosphate, ATP and PEP. Low or negligible activity was observed with glucose-1P, fructose-1P and phytic acid. The activity of the purified secreted acid phosphatase was stimulated by calcium and inhibited by molybdate, phosphate, fluoride, vanadate and nitrate. Activity was not inhibited by tartrate. The substrate profile and the biochemical properties suggest that Arabidopsis secreted acid phosphatase may have a role in mobilizing organic phosphate in the soil.