Plant Lipoxygenases – Structure and Mechanism of Biocatalysis

Abstract

Lipoxygenases (LOX; EC 1.13.11.12) catalyse regio- and stereospecific insertion of molecular oxygen into the (Z,Z)-penta-1,4-diene system of polyunsaturated fatty acids, producing fatty acid hydroperoxides. Plant lipoxygenases are involved in lipid degradation, regulation of growth and development, senescence and also in defense reactions of plants. Resolution of LOX crystal structure, determination of amino acid sequence in LOX proteins and steric properties of their active sites, spectrophotometric observation of cyclic changes in the iron oxidation state, and the radical formation in the catalysis resulted in the present knowledge of LOX catalytic mechanisms. The presence of several enzyme isoforms in the same cell and evidence of their different subcellular localization leads to the speculation that diverse isoforms could be involved in different branches of lipoxygenase metabolic pathways. Today, LOXs are studied as enzymes that take part in signal transduction processes in plant cells.