Purification and Properties of Acid Phosphatase from Plump and Shriveled Seeds of Triticale

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Abstract
A major triticale (X Triticosecale Wittmack) endosperm acid phosphatase (EC 3.1.2.2) (APase) from sib-lines producing plump and shriveled seed was purified 140- and 230-fold to a specific activity of 94 and 153 micromoles per minute per milligram protein respectively, by ammonium sulfate fractionation, ion-exchange chromatography, chromatofocusing, affinity column chromatography, and gel filtration. The purified enzyme from both materials is a monomeric glycoprotein with an apparent molecular weight of 45,700 .+-. 500 containing 12% carbohydrate and an apparent isoelectric point of pH 5.9. It hydrolyzes tri- and di-phosphate of nucleosides as well as phosphate esters and exhibits characteristics of ATP-hydrolyase and phosphatase. About 2-fold more of the APase was isolated from shriveled seeds, and the purified enzyme exhibited 3- and 5-fold higher Vmax for p-nitrophenyl phosphate and ATP, respectively, than that of plump seed. The I50 for Pi concentration was 5.5-fold higher in APase of shriveled seed than the plump one. These varied quantitative and kinetic properties substantiate the role of APase in lines with shriveled seeds being reduction of starch accumulation of depleting substrates and energy supply in the cytosol.