Background: Plant lipoxygenases (LOXs, EC 1.13.11.12) are involved in lipid degradation, regulation of growth and development, senescence, and defence reactions. LOX represents the starting enzyme of the octadecanoid pathway. The aim of the work was to purify LOX from California poppy (Eschscholtzia californica Cham.), to determine its biochemical properties and to identify and quantify the products of LOX reaction with unsaturated fatty acids. Methods: LOX from California poppy seedlings was purified by hydrophobic chromatography (Phenyl-Sepharose CL-4B) and by ion-exchange chromatography (Q-Sepharose). The isolated LOX was incubated with linoleic acid used as a substrate. The HPLC experiments were performed with the Agilent Technologies 1050 series HPLC system. For the preparative separation of a mixture of hydroxy fatty acids from the sample matrix, the RP-HPLC method was used (column 120-5 Nucleosil C18). Then, the NP-HPLC analysis (separation, identification, and determination) of hydroxy fatty acid isomers was carried out on a Zorbax Rx-SIL column. Results: The purified LOX indicates the presence of a nontraditional plant enzyme with dual positional specificity (a ratio of 9- and 13-hydroperoxide products 1:1), a relative molecular mass of 85 kDa, a pH optimum of 6.5, an increasing activity stimulation by CaCl₂ till 2 mM, and a high substrate reactivity to linoleic acid with kinetic values of K_M 2.6 mM and V_max 3.14 μM/min/mg. Conclusions: For the first time, the LOX from California poppy seedlings was partially purified and the biochemical properties of the enzyme were analyzed. A dual positional specificity of the LOX found from California poppy seedlings is in agreement with the results obtained for LOXs isolated from other Papaveraceaes. A 1:1 ratio of 9-/13-HODE is attractive for the simultaneous investigation of both biotic stress responses (indicated by the 9-HODE marker) and the biosynthesis of jasmonic acid and jasmonates (indicated by the 13-HODE marker).

Animal lipoxygenases (EC 1.13.11.12, LOX) convert arachidonic acid to biological active compounds known as eicosanoids. Proinflammatory eicosanoids - leukotrienes are involved in progression of atherosclerosis. Our attention was focused on a connection between activity of LOX and primary hypertriacylglycerolaemia, untreated or treated with fenofibrate. Our results show that LOX activity in the cytoplasm derived from liver of hypertriacylglycerolaemic rats is significantly increased (pH 7,2; relative to the control group), which may be one reason for more rapid atherosclerosis progression in lipid metabolism disorders. The highest LOX activity in microsomes was showed in groups of rats treated with fenofibrate. It appears that fibrates indirectly promote association of LOXs to membranes. In fat fraction no significant effect of hypertriacylglycerolaemia on the activity of lipoxygenase was found. Using gel electrophoresis significantly different spectrum of proteins was discovered in the control samples and samples of hypertriacylglycerolaemic rats. It appears that in condition of lipid metabolism imbalance formation of proteins with low molecular weight (and possibly also expression of LOX) is elevated.