CHEMICAL CHARACTERIZATION OF SELECTIVE INHIBITORS FOR A GLYCYRRHIZIN-BINDING LIPOXYGENASE FROM SOYBEANS

By GL-affinity column chromatography (HPLC), a GL-binding lipoxygenase (gbLOX) was selectively purified from a partially purified soybean LO X-1 fraction, gbLOX was identified as LOX-3 since the partial N-termin al amino acid sequences of at least four fragments generated from the purified gbLOX (p96 and p94) digested with trypsin were identical to t he corresponding sequences of soybean LOX-3, The inhibitory effects of various flavonoids and their modified derivatives, epigallocatechin g allate (EGCG) and a derivative (oGA) of glycyrrhetinic acid on the act ivities of two LOXs [gbLOX and ngLOX (non-GL-binding LOX)I were examin ed in vitro. It was found that (i) four compounds [quercetin, EGCG, a derivative (2',4'-DDC) of 3,4-dihydroxychalcone, and oGA] inhibit gbLO X activity in a dose-dependent manner, but do not affect ngLOX activit y; and (ii) quercetin as well as EGCG effectively prevents phosphoryla tion of gbLOX by casein kinase II (CK-II) in vitro, The results provid ed here suggest that the potent gbLOX inhibitors function as suppresso rs for the LOX3-catalyzed metabolic pathways in plant cells.