Purification and thermostability of isoperoxidase from oranges

Abstract

Soluble and ionically bound peroxidase were extracted from oranges ( citrus sinenis (L.) Osbeck cultivar Large Valencia, Small Sweet and Navel. Cationic and anionic isoperoxidase were obtained by Rotofor and ion-exchange chromatography. The pI for the soluble isoenzymes (4.5 to 9.0) was measured using a surface electrode and the M r (22 k to 44 k) was estimated by gel-filtration. The purified isoperoxidases (C 1 and C 2) were more heat stable than the peroxidase present in the crude extract. The inactivation of orange peroxidase activity in a mixture or individually in a purified state, was found to be non-linear with heating time.