Biochemical Characterization of Selective Inhibitors for a Glycyrrhizin-binding Lipoxygenase from Soybeans

Abstract

By GL-affinity column chromatography (HPLC), a GL-binding lipoxygenase (gbLOX) was selectively purified from a partially purified soybean LOX-1 fraction. gbLOX was identified as LOX-3 since the partial N-terminal amino acid sequences of at least four fragments generated from the purified gbLOX (p96 and p94) digested with trypsin were identical to the corresponding sequences of soybean LOX-3. The inhibitory effects of various flavonoids and their modified derivatives, epigallocatechin gallate (EGCG) and a derivative (oGA) of glycyrrhetinic acid on the activities of two LOXs [gbLOX and ngLOX (non-GL-binding LOX)] were examined in vitro. It was found that (i) four compounds [quercetin, EGCG, a derivative (2′, 4′-DDC) of 3, 4-dihydroxycitialcone, and oGA] inhibit gbLOX activity in a dose-dependent manner, but do not affect ngLOX activity; and (ii) quercetin as well as EGCG effectively prevents phosphorylation of gbLOX by casein kinase II (CK-II) in vitro. The results provided here suggest that the potent gbLO...