An acid phosphatase (EC 3.1.3.2) has been identified and purified from castor bean (Ricinus communis L., IAC-80) seed through sulphopropyl (SP)-Sephadex, diethylaminoethyl (DEAE)-Sephadex, Sephacryl S-200, and Concanavalin A-Sepharose chromatography. The enzyme was purified 2000-fold to homogeneity, with a final specific activity of 3.8 μkat mg-1 protein. The purified enzyme revealed a single diffuse band with phosphatase activity on nondenaturing polyacrylamide gel electrophoresis, at pH 8.3. The relative molecular mass, determined by high-performance liquid chromatography (HPLC), was found to be 60 kDa. The acid phosphatase had a pH optimum of 5.5 and an apparent K(m) value for p-nitrophenylphosphate of 0.52 mM. The enzyme-catalyzed reaction was inhibited by inorganic phosphate, fluoride, vanadate, molybdate, p-chloromercuribenzoate (pCMB), Cu2+ and Zn2+. The strong inhibition by pCMB, Cu2+ and vanadate suggests the presence of sulfhydryl groups essential for catalysis. The castor bean enzyme also recognized tyrosine-phosphate and inorganic pyrophosphate (PP(i)) as substrate. The highest specificity constant (V(max)/K(m)) was observed with PP(i), making it a potential physiological substrate.1072151158Barrett-Lennard, E.G., Robson, A.D., Greenway, H., Effect of phosphorus deficiency and water deficit on phosphatase activities from wheat leaves (1982) J Exp Bot, 33, pp. 682-693Basha, S.M., Purification and characterization of an acid phosphatase from peanut (Arachis hypogaea) seed (1984) Can J Bot, 62, pp. 385-391Biswas, T.K., Cundiff, C., Multiple forms of acid phosphatase in germinating seeds of Vigna sinensis (1991) Phytochemistry, 30, pp. 2119-2125Ching, T.M., Lin, T., Metzger, R.J., Purification and properties of acid phosphatase from plump and shriveled seeds of Triticale (1987) Plant Physiol, 84, pp. 789-795Conrad, F., Rüdiger, H., The lectin from pleurotus ostreatus: Purification, characterization and interaction with a phosphatase (1994) Phytochemistry, 30, pp. 277-283Duff, S.M.G., Lefebvre, D.D., Plaxton, W.C., Purification, characterization and subcellular localization of an acid phosphatase from Brassica nigra suspension cells. Comparison with phosphoenolpyruvate phosphatase (1991) Arch Biochem Biophys, 286, pp. 226-232Duff, S.M.G., Sarath, G., Plaxton, W.C., The role of acid phosphatases in plant phosphorus metabolism (1994) Physiol Plant, 90, pp. 791-800Ferreira, C.V., Granjeiro, J.M., Taga, E.M., Aoyama, H., Multiple forms of soybean seeds acid phosphatases (1998) Plant Physiol Biochem, 36, pp. 487-494Gellatly, K., Moorhead, G.B.G., Duff, S.M.G., Lefebvre, D.D., Plaxton, W.C., Purification and characterization of a potato tuber acid phosphatase having significant phosphotyrosine phosphatase activity (1994) Plant Physiol, 106, pp. 223-232Guo, J., Pesacreta, J.C., Purification and characterization of an acid phosphatase from the bulb of Allium cepa L., var. Sweet Spanish (1997) J Plant Physiol, 151, pp. 520-527Haraguchi, H., Yamauchi, D., Minamikawa, T., Multiple forms of acid phosphatase in cotyledons of Vigna mungo seedlings: Immunological detection and quantitation (1990) Plant Cell Physiol, 31, pp. 917-923Hartree, E.F., Determination of proteins: A modification of the Lowry method that gives a linear photometric response (1972) Anal Biochem, 48, pp. 422-427Hollander, V.P., Acid phosphatases (1971) The Enzymes, 4, pp. 449-498. , Boyer PD (ed) A. Academic Press, New York, NYHuyer, G., Liu, S., Kelly, J., Moffat, J., Payette, P., Kennedy, B., Tsaprailis, G., Ramachandran, C., Mechanism of inhibition of protein tyrosine phosphatase by vanadate and pervanadate (1997) J Biol Chem, 272, pp. 843-851Kawarasaki, Y., Nakano, H., Yamane, T., Purification and some properties of wheat germ acid phosphatase (1996) Plant Sci, 119, pp. 67-77Kruzel, M., Morawiecka, B., Acid phosphatase of potato tubers (Solanum tuberosum L.). Purification, properties, sugar and amino acid composition (1982) Acta Biochim Pol, 29, pp. 321-330Lebansky, B.R., McKnight, T.D., Griffing, L.R., Purification and characterization of a secreted purple phosphatase from soybean suspension cultures (1992) Plant Physiol, 99, pp. 391-395Lowry, O.H., Lopez, J.A., The determination of inorganic phosphate in the presence of labile phosphate esters (1945) J Biol Chem, 162, pp. 421-424Pan, S., Characterization of multiple acid phosphatase in salt, stressed spinach leaves (1987) Aust J Plant Physiol, 14, pp. 117-124Panara, F., Pasqualini, S., Antonielli, M., Multiple forms of barley root acid phosphatase: Purification and some characteristics of the major cytoplasmic isoenzyme (1990) Biochim Biophys Acta, 1037, pp. 73-80Park, H.S.C., Van Etten, R.L., Purification and characterization of homogeneous sunflower seed acid phosphatase (1986) Phytochemistry, 25, pp. 351-357Penheiter, A.R., Duff, S.M.G., Sarath, G., Soybean root nodule acid phosphatase (1997) Plant Physiol, 114, pp. 597-604Polya, G.M., Wetlenhall, R.E.H., Rapid purification and N-terminal sequencing of a potato tuber cyclic nucleotide binding phosphatase (1992) Biochim Biophys Acta, 1159, pp. 179-184Reisfeld, R.A., Lewis, V.J., Williams, D.E., Disk electrophoresis of basic proteins and peptides on polyacrylamide gels (1962) Nature, 195, pp. 281-283Staswick, P.E., Papa, C., Huang, J., Rhee, Y., Purification of the major soybean leaf acid phosphatase that is increased by seed. Pod removal (1994) Plant Physiol, 104, pp. 49-57Swarup, G., Cohen, S., Garbers, D.L., Inhibition of membrane phosphotyrosyl protein phosphate activity by vanadate (1982) Biochem Biophys Res Commun, 107, pp. 1104-1109Taga, E.M., Van Etten, R.L., Human liver acid phosphatase: Purification and properties of a low, molecular weight isoenzyme (1982) Arch Biochem Biophys, 214, pp. 505-515Ullah, A.H.J., Gibson, D.M., Purification and characterization of acid phosphatase from cotyledons of germinating soybean seeds (1988) Arch Biochem Biophys, 260, pp. 514-520Yumagata, H., Tanaka, K., Kasai, Z., Purification and characterization of acid phosphatase in aleurone particles of rice grains (1980) Plant Cell Physiol, 21, pp. 1449-1460Yupsanis, T., Eleftheriou, P., Pantazaki, A., Georgatsos, J.G., Multiplicity of metal independent protein phosphatases of germinated alfafa seeds (1993) J Plant Physiol, 141, pp. 257-262