الفهرس 
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Abstract
Acid phosphatase from the cotyledons of sunflower expressed maximum activity at the 5th day of germination. Gibberellic acid, indol-3-acetic acid and jasmonic acid induced acid phosphatase activity. NaCl, CdCl2 and PbCl2 reduced acid phosphatase activity. Acid phosphatase was purified using ammonium sulphate, DEAE-cellulose column, Sephadex G200 and Sephacryl S300 with final specific activity of 75 units mg-1 protein. P-nitrophenol phosphate was the substrate of acid phosphatase. The enzyme was inhibited by the various tested protein inhibitors: Furd, cordycepin and α-amanitin.. The polyols namely: mannitol, glycerol protected the enzyme from inactivation at 70ºC. Both the free and immobilized acid phosphatase was stable against digestion by pepsin and trypsin. The results show that, both arginyl, -SH and histidyl groups are essential for acid phosphatase catalysis.