This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Riov, J. Search for Related Content PubMed PubMed Citation Articles by Riov, J. Agricola Articles by Riov, J.

Articles

Metabolism of Uronic Acids in Plant Tissues

Partial Purification and Properties of Uronic Acid Oxidase from Citrus Leaves ¹

^a Department of Horticulture, The Hebrew University of Jerusalem, Rehovot, Israel

A new enzyme, named uronic acid oxidase, was extracted and purified 67-fold by (NH₄)₂SO₄ fractionation and CM-Sephadex column chromatography from ethylene-treated Shamouti orange (Citrus sinensis L. Osbeck) leaves. The enzyme catalyzes the oxidation of D-galacturonic acid and D-glucuronic acid to the corresponding hexaric acids in the presence of molecular oxygen with the production of H₂O₂. The pH optimum for the oxidation of D-galacturonic acid and D-glucuronic acid is between 7 and 8. The enzyme is highly specific for D-galacturonic acid and D-glucuronic acid. It also oxidizes polygalacturonic acid. The apparent Michaelis constant values of the enzyme for D-galacturonic acid and D-glucuronic acid are 0.13 and 0.5 mM, respectively. The molecular weight of the enzyme, as determined by gel filtration, is about 98,000. The enzyme is inhibited by sodium hydrosulfite and other sulfites, indicating that it contains a flavin prosthetic group.

¹ This work was supported in part by a grant from the Bat-Sheva de Rotschild Fund for the Advancement of Science and Technology.