Purification and properties of ascorbate free-radical reductase from potato tubers.

Ascrobate free-radical reductase (EC 1.6.5.4) from potato tubers was purified to apparent homogencity by a method which included ammonium-sulfate precipitation, gel filtration and chromatography on diethylaminoethyl cellulose and hydroxylapatite. Gel filtration and gel electrophoresis showed that the purified enzyme was monomeric with a molecular weight of about 42 000. Enzyme activity was heat lable and severely inhibited by thiol reagents. The Km values for enzyme substrates were estimated.