Characterization of cell-wall-bound nuclease and ribonuclease from potato tuber.

Two enzymes, a nutlease and a ribonuclease (RNase) were isolated from the cell walls of potato tubers. The nuclease was purified by 1370-fold fractionation with ammonium sulfate and chromatography on Sephadex G-200 and DEAE-Sephadex A-50 columns. The purified nuclease hydrolysed both RNA and DNA, yielding primarily purine 5'-nucleotides. The ribonuclease did not cleave DNA and the hydrolysis of RNA produced 2':3'-cyclic nucleotides as products. Both enzymes were inhibited by Cu2+ and Zn2+, while EDTA inhibited the nuclease and promoted the RNase. The cell wall enzymes are different from the corresponding cytoplasmic enzymes previously characterized [T. T. Nguyen, M. M. Palcic and D. Hadziyev, J. Chromatogr., 388, 189 (1987)] with respect to pH and temperature optima and molecular weights.