RESUMO
Lipoxygenases are widespread plant enzymes that catalyze the peroxidation of polyunsaturated fatty acids. This reaction is pivotal in the enzymatic cascade that leads to production of numerous metabolism regulators named oxylipins. The activity of these biologically active substances is directly associated with defence reactions in conditions of biotic and abiotic stresses as well as with the regulation of plant growth, propagation and senescence. In this review the contemporary notions about lipoxygenases classification, structure and catalytic properties are summarized. The features of enzyme activity regulation by transcriptional and posttranslational mechanisms in addition to the role of lipoxygenase catalysis in plant cell signalling are discussed.
Assuntos
Regulação da Expressão Gênica de Plantas , Lipoxigenases/metabolismo , Oxilipinas/metabolismo , Células Vegetais/enzimologia , Proteínas de Plantas/metabolismo , Plantas/enzimologia , Adaptação Fisiológica , Peroxidação de Lipídeos , Lipoxigenases/química , Lipoxigenases/genética , Modelos Moleculares , Proteínas de Plantas/química , Proteínas de Plantas/genética , Plantas/genética , Processamento de Proteína Pós-Traducional , Transdução de Sinais , Estresse Fisiológico , Transcrição GênicaRESUMO
The inhibiting effects of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its 4-substituted derivatives in reactions of linoleyl acid or linoleyl alcohol oxidation catalyzed by potato tuber 5-lipoxygenase were investigated. Inhibiting properties of stable nitroxyl radicals in presence of lubrol and SDS were reduced at the transition from TEMPO to 4-hydroxy-TEMPO or 4-amino-TEMPO and increased at use of adamantane-1-carboxylic or 3-methyladamantane-1-carboxylic acid 1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl esters. Enzyme activity at saturating concentrations of inhibitor was not suppressed completely, and decreased up to the certain level determined by the substrate nature. The dependence of partial inhibition efficiency on rotational correlation time of stable nitroxides in model micellar systems were analysed. It was supposed that 5-lipoxygenase inhibition includes the interaction of hydrophobic nitroxide with radical intermediate formed in enzymatic process.
Assuntos
Araquidonato 5-Lipoxigenase/química , Óxidos N-Cíclicos/química , Álcoois Graxos/química , Ácido Linoleico/química , Óxidos de Nitrogênio/química , Araquidonato 5-Lipoxigenase/isolamento & purificação , Catálise , Cinética , Estrutura Molecular , Oxirredução , Solanum tuberosum/químicaRESUMO
The linoleyl alcohol oxidation catalyzed by potato tuber 5-lipoxygenase was found to be efficiently inhibited by stable nitroxyl radicals: 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 1-bicyclo[2,2,2]octane-1-carboxylate, 1-adamantylacetate, dodecanoate, and octadecanoate. The dependence of apparent IC50 values on the rotational correlation times of times of 4-hydroxy-1-oxyl-2,2,6,6-tetramethylpiperidine and its derivatives in model micellar systems was analyzed. The inhibition mechanism was proposed; it involves the interaction of hydrophobic nitroxyl radical with the intermediate radical enzyme-substrate complex.
