Purification and Properties of Acid Phosphatase-1 from a Nematode Resistant Tomato Cultivar

In tomato the acid phosphatase-1 isozyme (Apase-1) is inherited as a single locus linked to the nematode resistance gene (Mi). The Apase-1(1) electrophoretic variant has been purified from a tomato cell suspension culture using ion exchange and concanavalin A sepharose affinity chromatography. A cellulose acetate electrophoresis method was used to distinguish Apase-1(1) rapidly from other Apase isozymes in tomato. The subunit molecular weight of the purified enzyme was estimated to be 31,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The native size of the enzyme, which is reported to be a dimer, was determined to be approximately 51,000 by high performance liquid chromatography gel filtration. Apase-1(1) has a lower pH optimum and a distinct substrate specificity as compared to Apases extracted from tomato fruit or from other plant species. The amino acid composition of Apase-1(1) is similar to that of a potato Apase.