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 Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (100) Citing Articles via Google Scholar Google Scholar Articles by Dalton, D. A. Articles by Evans, H. J. Search for Related Content PubMed PubMed Citation Articles by Dalton, D. A. Articles by Evans, H. J. Agricola Articles by Dalton, D. A. Articles by Evans, H. J.

Metabolism and Enzymology

Purification, Properties, and Distribution of Ascorbate Peroxidase in Legume Root Nodules ¹

Laboratory for Nitrogen Fixation Research, Oregon State University, Corvallis, Oregon 97331

All aerobic biological systems, including N₂-fixing root nodules, are subject to O₂ toxicity that results from the formation of reactive intermediates such as H₂O₂ and free radicals of O₂. H₂O₂ may be removed from root nodules in a series of enzymic reactions involving ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. We confirm here the presence of these enzymes in root nodules from nine species of legumes and from Alnus rubra. Ascorbate peroxidase from soybean nodules was purified to near homogeneity. This enzyme was found to be a hemeprotein with a molecular weight of 30,000 as determined by sodium dodecyl sulfate gel electrophoresis. KCN, NaN₃, CO, and C₂H₂ were potent inhibitors of activity. Nonphysiological reductants such as guaiacol, o-dianisidine, and pyrogallol functioned as substrates for the enzyme. No activity was detected with NAD(P)H, reduced glutathione, or urate. Ascorbate peroxidation did not follow Michaelis-Menten kinetics. The substrate concentration which resulted in a reaction rate of V_max was 70 micromolar for ascorbate and 3 micromolar for H₂O₂. The high affinity of ascorbate peroxidase for H₂O₂ indicates that this enzyme, rather than catalase, is responsible for most H₂O₂ removal outside of peroxisomes in root nodules.

¹ Supported by National Science Foundation Grant DMB 85-13846 and by the Oregon Agricultural Experiment Station from which this is Technical Paper No. 7997.

This article has been cited by other articles:

				C. Chang, I. Damiani, A. Puppo, and P. Frendo Redox Changes during the Legume-Rhizobium Symbiosis Mol Plant, May 1, 2009; 2(3): 370 - 377. [Abstract] [Full Text] [PDF]

				M. A. Matamoros, J. Loscos, M. J. Coronado, J. Ramos, S. Sato, P. S. Testillano, S. Tabata, and M. Becana Biosynthesis of Ascorbic Acid in Legume Root Nodules Plant Physiology, July 1, 2006; 141(3): 1068 - 1077. [Abstract] [Full Text] [PDF]

				S. Sano, M. Ueda, S. Kitajima, T. Takeda, S. Shigeoka, N. Kurano, S. Miyachi, C. Miyake, and A. Yokota Characterization of Ascorbate Peroxidases from Unicellular Red Alga Galdieria partita Plant Cell Physiol., April 1, 2001; 42(4): 433 - 440. [Abstract] [Full Text] [PDF]

				D. A. Dalton, S. L. Joyner, M. Becana, I. Iturbe-Ormaetxe, and J. M. Chatfield Antioxidant Defenses in the Peripheral Cell Layers of Legume Root Nodules Plant Physiology, January 1, 1998; 116(1): 37 - 43. [Abstract] [Full Text]