PURIFICATION OF POLYPHENOL OXIDASE FREE OF THE STORAGE PROTEIN PATATIN FROM POTATO-TUBER

Routine protein purification to homogeneity from potato tuber, as from other storage tissues and seeds, is often hindered due to the large a mounts of storage protein present. In potato, patatin, the major stora ge protein of the tuber, often contaminates preparations. The present work describes the purification of polyphenol oxidase (PPO) from the p otato tuber (Solanum tuberosum cv Cara) to homogeneity including the c ritical step of hydrophobic chromatography on Octyl-Sepharose which wa s sufficient to completely remove patatin. The purified PPO was found to be a doublet of M(r) 60 000 and 69 000 when analysed by SDS-PAGE wi th a K-m 4.3 +/- 0.3 mM for L-dihydroxyphenylalanine. Both bands were found to have similar N-termini corresponding to PPO isoforms when seq uenced.