Cantu, D., Department of Agricultural Sciences and Technologies, University of Milan, Milan, Italy
Greve, L.C., Department of Plant Sciences, University of California, Davis, CA 95616, United States
Lurie, S., Department of Postharvest Science, Volcani Center, ARO, Bet Dagan 50250, Israel
Labavitch, J.M., Department of Plant Sciences, University of California, Davis, CA 95616, United States

Uronic acid oxidase activity was found in an extract from harvested peaches that was incubated with citrus pectin at pH 8.5. The product of this reaction was identified by GC-MS analysis to be galactaric acid. The reaction was linear at 37°C for up to 20 h, and the pH optimum was 8.5. The activity found in firm peaches one day after harvest did not change as the peaches softened over 5 days to eating softness. The incubation conditions were those suitable for monitoring the activity of pectate lyase, but instead of finding an increase in galacturonosyl residue reducing groups due to generation of pectin-derived oligosaccharides, uronic acid oxidase catalyzed the oxidation of the aldehyde reducing functions to carboxyl groups. © 2005 Elsevier Ltd. All rights reserved.