p-Nitrosodimethylaniline (RNO) bleaching by soybean lipoxygenase-1. Biochemical characterization and coupling with oxodiene formation

• Published in: Plant physiology and biochemistry Vol. 38; no. 11; pp. 845 - 852
• Main Authors: Pastore, D. (Universita del Molise, Campobasso (Italie). Facolta di Agraria, Dipartimento di Scienze Animali Vegetali e dell' Ambiente), Trono, D, Padalino, L, Di Fonzo, N, Passarella, S
• Format: Journal Article
• Language: English
• Published: Paris Elsevier 01.11.2000
• Subjects: ACIDE LINOLEIQUE; ACIDO LINOLEICO; Agronomy. Soil science and plant productions; BIOCHEMISTRY; BIOCHIMIE; Biological and medical sciences; BIOQUIMICA; Economic plant physiology; Enzymes; Fundamental and applied biological sciences. Psychology; GLYCINE MAX; LINOLEIC ACID; LIPOXIGENASA; LIPOXYGENASE; Metabolism; Nutrition. Photosynthesis. Respiration. Metabolism; ORGANIC ACID SALTS; Plant physiology and development; PLANTAS PROTEAGINOSAS; PLANTE PROTEAGINEUSE; PROTEIN PLANTS; SALES DE ACIDOS ORGANICOS; SEL D'ACIDE ORGANIQUE; Nitroso compound; Enzyme; Metabolic pathway; Glycine max; Characterization; Grain legume; Enzymatic activity; Leguminosae; Bleaching; Dicotyledones; Angiospermae; Spermatophyta; Oxidoreductases; Lipoxygenase; Catalyst activity
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/S0981-9428(00)01194-3

In this paper, a novel reaction catalysed by the soybean lipoxygenase-1 (linoleate:oxygen oxidoreductase, EC 1.13.11.12) (LOX-1) is reported: p-nitrosodimethylaniline (RNO) bleaching. RNO bleaching in the course of the LOX-1 reaction (with linoleate as substrate) was followed by monitoring photometrically at 440 nm the absorbance decrease of the test sample. The appearance of osodienes, a class of compounds produced during the same reaction, was also studied. This was carried out by monitoring the absorbance increase at 285 nm in the course of the LOX-1 reaction. RNO bleaching and oxodiene formation by soybean LOX-1 were found to occur synchronously. They occurred only under conditions of limited oxygen; moreover, both reactions showed saturation kinetics as expected for enzyme-catalysed reactions , had similar dependence on pH and temperature (pH optima about 9, temperature optima about 45 degrees C) and were competitively inhibited by n-propylgallate (PG), a free radical scavenger. Finally, the occurrence of both reactions was found to depend on the presence of 13-hydroperoxy-linoleate, the primary product of the aerobic LOX reaction and was found to be not related with the beta-carotene bleaching catalysed by the same enzyme. The possible molecular basis of the link between RNO bleaching and oxodiene formation in the course of the anaerobic soybean LOX-1 reaction is discussed.