OXIDATION OF [1-C-14]LINOLEIC ACID IN ISOLATED MICROSOMES FROM PEA LEAVES

The oxidation of [1-14C]linoleate in isolated microsomes from pea leaves was found to be stimulated by NADPH addition. The formation of one of the main metabolites, 12-hydroxy-9(Z)-dodecenoic acid is particularly NADPH-dependent. The predominant products in the absence of NADPH were hydroperoxides and in the presence of NADPH, 12-hydroxy-9(Z)-dodecenoic acid. Exogenous [1-14C]-13-hydroperoxy-9(Z), 11(E)-octadecadieoic acid and [1-14C]-12-oxo-9(Z)-dodecenoic acidwere the efficient precursors of 12-hydroxy9(Z)-dodecenoic acid. It was concluded that 12-hydroxy-9(Z)-dodecenoic acid is formed by NADPH-dependent enzymatic reduction of 12oxo-9(Z)-dodecenoic acid. The observed inhibition of linoleate oxidation in isolated microsomes by CO and metryapone suggests the involvement of cytochrome P-450 in the reaction. The relative contribution of lipoxygenase and monooxygenase activity to linoleate oxidation in microsomes is discussed. © 1990.