Isolation and partial characterization of cytoplasmic and wall-bound acid phosphatases from wheat roots

Abstract

In wheat (Triticum aestivum) roots, about 67% of the total activity of acid phosphatase was associated with the cell wall debris, and 35% of it was released from the wall by incubation with 0.8 M NaCl overnight. Three major cytoplasmic and two major wall-bound acid phosphatases were then separated by gel filtration on Sephadex G-75 and ion-exchange chromatography on carboxymethyl cellulose, and some of their characteristics were compared. They showed maximum activities in the same pH range (4.7–5.0) and had broad substrate specificities. They all showed high activity toward ADP. followed by ATP, glucose-6-phosphate, and creatine phosphate and much less activity toward AMP, glucose-1-phosphate, fructose-1,6-diphosphate, and ribose-5-phosphate. The wall-bound enzymes were more active to ADP and ATP than those of the cytoplasm. Mg2+, Ni2+, NaCN, and EDTA had no appreciable effects on the enzymatic activities. However, all enzymes were strongly inhibited by Hg2+ and Fe3+ and, to varied degrees, by Cu2+, Zn2+, Co2+, NaF. p-chloromercuribenzoate, and urea in that order. The molecular weights, estimated by sodium dodecylsulfate gel electrophoresis, ranged from 28 000 to 64 000.