Plant lipoxygenases (lox) catalyze the oxygenation of polyunsaturated fatty acids with a 1,4-cis, cis-pentadiene structure to form conjugated diene hydroperoxides. These in turn can be converted into a variety of secondary metabolites by an array of enzymes. The physiological function of lox is only poorly understood. In barley two isoenzymes have been described, namely lox-1 and lox-2, which clearly differ in properties, e.g. products formed from linoleic acid [1,3,4]. This suggests that lox-1 and lox-2 each give rise to different lipoxygenase pathway end-products and fulfil distinct physiological roles in the germinating kernel. To get more insight into these roles we have performed a detailed study on the expression of lox-1 and lox-2 during germination at the activity, protein and mRNA level. Additionally, kinetic data are presented concerning the specificity of lox-1 and lox-2 towards different substrates.
