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Tao Wu and Jiashu Cao

Peroxidases (EC have many physiological roles in several primary and secondary metabolic processes, such as scavenging of peroxide, participation in lignification, regulation of cell growth and differentiation, hormonal signaling, plant

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L. Mark Lagrimini, Jill Vaughn, John Finer, Karen Klotz, and Patrick Rubaihayo

Abbreviations: CaMV, cauliflower mosaic virus; POD, peroxidase; TobAnPOD, tobacco anionic peroxidase. 1 Dept. of Horticulture, to whom reprint requests should be addressed. 2 Dept. of Food Science and Technology. 3 Dept. of Agronomy. 4 Dept. of

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M.G. DeWald, G.A. Moore, and W.B. Sherman

Abbreviations: F, fast band; FF, fast-migrating band; FS, fast- and slow-migrating bands; PER, peroxidase; PGM, phosphoglucomutase; PI, plant introduction; S, slow band; SOD, superoxide dismutase; SS, slow-migrating band. 1 To whom reprint requests

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T.J. Miesle, A. Proctor, and L.M. Lagrimini

Abbreviation: POD, peroxidase. 1 Graduate student, Dept. of Food Science and Technology. 2 Assistant Professor, Dept. of Food Science and Technology, to whom reprint requests should be addressed. 3 Assistant Professor, Dept. of Horticulture

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T.G. McCollum and R.E. McDonald

Grapefruit (Citrus paradisi) flavedo is a rich source of peroxidase (POD) (EC Changes in POD have been related to senesence and environmental stress in a variety of plant tissues. However, due to the large number of POD isoenzymes as well as the broad substrate specificity, measurement of POD activity in crude extracts is of limited value for gaining an understanding of the role of POD in vivo. We have begun to purify and characterize POD isoenzymes from grapefruit flavedo. HPLC gel permeation chromatography reveals 2 peaks of POD activity with apparent MW of 66 kD and 30 kD. Native PAGE (8% bis-acrylamide, pH 8.8) followed by activity staining indicates that the PODs differ in Pi; the 30 kD POD migrates anodally, whereas the 66 kD POD does not migrate. Isoelectric focusing has been used to separate flavedo PODs into acid (Pi ca 4.0) and basic (Pi > 8.5) forms. Treatment of grapefruit with ethylene (2 ppm 72 hours) induces a basic POD not present in freshly-harvested fruit or in nonethylene-treated controls.

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Huai-Fu Fan, Wen Chen, Zhou Yu, and Chang-Xia Du

Peroxidases, which comprise an important class of oxidoreductases, are widely distributed in all living organisms. PODs use H 2 O 2 as their electron acceptor and iron porphyrin as their prosthetic group to catalyze substrate oxidation ( Valério et

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J.K. Collins, C. Biles, E.V. Wann, and P. Perkins-Veazie

Increased peroxidase activity is used to predict development of off-flavor in frozen sweet corn. However, peroxidase activity was not indicative of flavor changes in frozen supersweet (sh2) or sugar enhanced (sul/se) sweet corn genotypes. These results suggested an inactivation or absence of certain peroxidase isozymes. Frozen `Florida Staysweet' (sh2), `Merit' (sul), and `Bodacious' (sul/se) kernels were cut from cobs after 0 and 12 months of storage. Proteins extracted from acetone powders were separated by isoelectric focusing (IEF) and Native-PAGE. Banding patterns differed according to cultivar and storage duration. All cultivars contained a peroxidase isozyme having a molecular weight of 99 kD and pI of 4.5. The sul/se and su2 cultivars expressed an additional peroxidase band of 17.9 kD. An additional peroxidase isozyme (pI 5.0) appeared after 12 months of storage in the sul cultivar. This isozyme did not appear in sul/se or sh2 and is a possible marker for predicting off-flavor in corn. This isozyme may also catalyze off-flavor reactions in sul corn genotypes. Although changes in total peroxidase activity may not predict flavor loss in all genotypes, certain peroxidase isozymes may be useful in predicting and catalyzing off-flavor reactions in sul corn cultivars.

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Olfa Zarrouk, Pilar S. Testillano, María Carmen Risueño, María Ángeles Moreno, and Yolanda Gogorcena

union ( Hartman et al., 2002 ). The peroxidase enzyme is associated with differentiating xylem ( Sterjiades et al., 1993 ), as well as with lignification processes ( Harkin and Obst, 1973 ). In addition, this enzyme was reported to be implicated in

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Pedro Novillo, Alejandra Salvador, Pilar Navarro, and Cristina Besada

., 2003 ). The ROS metabolism is controlled by an array of interrelated enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD), which act concomitantly with nonenzymatic antioxidants; O 2 − is

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Mosbah M. Kushad, Nadeem A. Abbasi, Chunlin Xiao, and A. Bratsch

Peroxidases are an enzyme family that displays a wide range of forms, functions, and distribution in the plant kingdom. Peroxidase extracted from horseradish is one of a few enzymes that had been widely used in industrial and clinical research. Horseradish peroxidase (HRP, EC, donor: hydrogen-peroxide oxidoreductase) has been used to estimate the levels of other enzymes, in immunoassay, bio-bleaching processes, and in lignin degradation for fuel production. Despite its extensive use, little is known about HRP distribution in horseradish plants. Four commercial horseradish cultivars (IL-647, IL-1069, IL-1573, and IL-1590) were evaluated for HRP activity in the main root, lateral roots, leaves, and leaf blades. HRP activity was highest in the main root followed by lateral roots. However, only a trace amount of HRP activity was detected in leaf blade and leaf petiole. IL-1573 has the highest HRP activity, while IL-647 has the lowest activity. Site of HRP synthesis and its distribution during horseradish plant growth and development will be described.