Localization and activity of lipoxygenase in Cd-treated seedlings of Phaseolus coccineus

Ewa Skórzyńska-Polit,Ewa Szczuka,Andrzej Plak,Bożena Pawlikowska-Pawlęga,Jerzy Melke

doi:10.5586/asbp.2005.026

Ewa Skórzyńska-Polit, Ewa Szczuka + Show 3 more

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https://doi.org/10.5586/asbp.2005.026

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Abstract

Lipoxygenase was localized in the primary leaves of <em>Phaseolus coccineus</em> (L.), seedlings treated with 25 µM Cd and in control plants using the immunogold method. The enzyme was localized mainly in the peripheral parts of protoplast of control plant cells. It was found in the cell wall, along the ER elements, at plastid lamellae and inside the mitochondria. In Cd-treated seedlings the elements of parenchyma cells showed an atypical inner structure. The immunolabelling of LOX was less intensive in comparison with control. The enzyme was found in the cytoplasm, at the cell wall area, vacuoles and in the plastid stroma as single gold particles. LOX activity optima were determined at pH 7.0 and 8.0 for both linoleic and linolenic acid used as substrates. After 2 days of seedlings exposure to Cd the activity of LOX decreased at pH 7.0 and 8.0 when linoleic acid was used as substrate, and strongly declined at pH 7.0 after 4 days of the metal treatment. When linolenic acid was the substrate LOX activity slightly increased after 2 days of the plants exposure to Cd, but after 4 days it rapidly decreased at pH 7.0. The changes in LOX activity are discussed.

Highlights

Lipoxygenases (LOXs; EC 1.13.11.12) are a large family of enzymes which catalyze the dioxygenation of the long chain of fatty acids containing cis, cis-1,4-pentadiene structure to hydroperoxides (Maccarrone et al 1994; Feussner and Wasternack 2002)
In etiolated 5-day-old seedlings of Phaseolus coccineus the parenchyma tissue of young primary leaves consisted of elongated cells surrounded by thin walls
Positive immunoreaction to LOX was more intensive in the cytoplasm the immunogold particles were observed in the cell wall area (Fig. 2)

Summary

Introduction

Lipoxygenases (LOXs; EC 1.13.11.12) are a large family of enzymes which catalyze the dioxygenation of the long chain of fatty acids containing cis, cis-1,4-pentadiene structure to hydroperoxides (Maccarrone et al 1994; Feussner and Wasternack 2002). Polyunsaturated long chain fatty acids as linoleic and a-linolenic acid are ideal substrates for lipoxygenase (Siedow 1991), and further reactions of hydroperoxides are known as lipoxygenase pathway or octadecanoic pathway (Gardner 1995). LOX strongly prefers free fatty acids as substrates, but its activity with polyunsaturated fatty acids (PUFAs) estrified to phospholipids and with PUFAs estrified in neutral lipids such as triglycerides was found (Feussner et al 2001; Stelmach et al 2001; see Feussner and Wasternack 2002). Lipoxygenases occur in plants in various isoforms. They may differ in their properties, kinetic parameters or sub- Most plant lipoxygenase isoenzymes hydroperoxidize polyunsaturated fatty acids in a stereo-specific manner giving either 13(S)- or 9 (S)-hydroperoxides, and some yield a mixture of both (Gardner 1995)

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