COMPARISON OF CHARACTERISTICS OF ACID-PHOSPHATASES SECRETED FROM ROOTS OF LUPIN AND TOMATO

In this study me purified both acid phosphatases (Apase) secreted from tomato and lupin roots, and compared the properties of these two enzy mes. The secretory Apases from tomato and lupin showed the following s imilar properties, 1) Both enzymes were homodimers consisting of two i dentical subunits, each with a molecular weight of approximately 68 ki lodaltons (kD) in tomato and 72 kD in lupin. 2) The enzymes were stabl e in the pH range of 4-9. 3) The enzymes showed an optimum temperature of 37-40 degrees C for their activity and were stable at temperatures below 60 degrees C. 4) The enzymes exhibited a comparable affinity fo r p-nitrophenyl phosphate (the apparent K-m values mere 2.7-3.0 x 10(- 5) M). On the other hand, there were some slight differences in the is oelectric point, optimum pH, specific activity, substrate specificity, and inhibitory effect of metal ions between the two enzymes. Therefor e, it was considered that the most important difference in the root ab ility of the two plants to hydrolyze organic phosphorus may depend mai nly on the amount of Apase secreted from a unit amount of roots.