Inhibitory effects of green tea catechins and their derivatives on the matrilysin-catalyzed hydrolysis of a synthetic substrate, (7-methoxycoumarin-4-yl)acetyl-L-Pro-L-Leu-Gly-L-Leu-[N(3)-(2,4-dinitrophenyl)-L-2,3-diamino-propionyl]-L-Ala-L-Arg-NH(2) [MOCAc-PLGL(Dpa)AR], were examined. The 10 catechins examined were classified into three groups according to their inhibition potency. Catechins with a galloyl group at the 3 position, including a major component of green tea catechin, (-)-epigallo-3-catechin gallate [(-)-EGCG], were the most potent inhibitors and inhibited matrilysin in a non-competitive manner with K(i) values of 0.47-1.65 micro M. The inhibitory potency of (-)-EGCG was not influenced by the presence of an inhibitor, ZnCl(2), suggesting that the inhibitions of matrilysin by (-)-EGCG and by ZnCl(2) might be independent of each other. The inhibitory effects of green tea catechins suggest that a high intake of green tea might be effective for the prevention of tumor metastasis and invasion in which matrilysin is concerned.

To utilize soy protein isolate (SPI) more widely, a convenient and effective method for deodorizing it is required. This paper reports a new deodorizing method using various types of solid adsorbents made of polystyrene, polymethacrylate, and zeolite, as well as charcoal. Treatment of the SPI solution with them decreased the hexanal content in the solution, whereas the content of linoleic acid was not much decreased. A brominated polystyrene adsorbent (SEPABEADS SP207) and a zeolite adsorbent (HSZ-360HUD) removed hexanal most effectively, although 30-40% of the total hexanal remained. A model experiment showed that their hexanal adsorption capacity was much higher than the hexanal content in the SPI solution and that an excess amount of hexanal added to the SPI solution was mostly removed by them. These results suggest that hexanal in the SPI solution can be classified into two types. Hexanal of type I may be free or bound weakly on the surface of proteins and is removable by the adsorbents, whereas hexanal of type II may be bound tightly inside proteins and is unremovable by the adsorbents. Despite the considerable amount of hexanal remaining in the SPI solution even in the most successful cases, the SPI solution was well deodorized as shown by the sensory test. Accordingly, type I hexanal may be closely related to the soybean odor. Removal of hexanal by the adsorbents was not much improved by alpha-chymotryptic digestion of SPI. Type II hexanal might be in similar states even in the chymotryptic digests.

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MMPs are considered to be involved in the tumor metastasis and invasion, and potent and safe MMP inhibitors have been desired for tumor therapy. The inhibitors could be also useful tool to regulate the enzyme activity and to explore the enzyme reaction mechanism. In this study, inhibitory effect of 10 catechins and 9 dibenzylbutyrolactone lignans on MMP-7 activity was examined in the hydrolysis of a synthetic substrate, MOCAc-PLGL(Dpa)AR, in 50 mM HEPES buffer (pH 7.5) containing 10 mM CaCl2. The catechins examined were classified into three groups according to their inhibition potency: (+) and (-)-catechins, and (+) and (-)-epicatechins (EC) had Ki of > 1 mM; (-)-gallocatechin (GC) and (-)-epigallocatechin (EGC) had Ki of > 0.05 mM; and catechins with a galloyl group at the 3 position [(-)-catechin-3-gallate (CG), (-)-epicatechin-3-gallate (ECG), (-)-gallocatechin-3-gallate (GCG), and (-)-epigallocatechin-3-gallate (EGCG)] had Ki values of 400-1600 nM. The inhibitory potency of ECG was the strongest among them. A major component of green tea chatechin, EGCG, is in the third group. The inhibition manner of the catechins in the third group against MMP-7 was shown to be non-competitive. The potency of EGCG was not affected by the presence of an inhibitor ZnCl2, suggesting that the inhibitions of MMP-7 by EGCG and by ZnCl2 might be independent of each other. The inhibitory effects of green tea catechins suggest that a high intake of green tea might be effective for the prevention of tumor metastasis and invasion in which MMP-7 is concerned. All of the lignans examined inhibited MMP-7 with the IC50 ranging from 0.05 to >0.28 mM. Matairesinol, which has the basic structure of the other lignans, showed the weakest inhibition. Lignans with methylenedioxy ring(s) or a hydroxyl group at the C5-position inhibited MMP-7 more strongly than matairesinol. 5-Hydroxypluviatolide, which has both a methylenedioxy ring and a hydroxyl group at the C5-position, was the most potent inhibitor (IC50 = 0.05 mM), suggesting that the introduction of these two elements might enhance synergistically the inhibitory activity of lignans. 5-Hydroxypluviatolide inhibited MMP-7 in a competitive manner, and its inhibitory effect was greatly suppressed by the presence of another competitive inhibitor, dimethyl sulfoxide. The precursors of matairesinol, coniferyl alcohol and secoisolariciresinol, had no inhibitory activity, indicationg that the dibenzylbutyrolactone structure is essential for the inhibition. Lignans were shown to have the potential to inhibit MMP-7, and the knowledge of their structure-function relationship might be beneficial to developing selective inhibitors for MMPs. It should be noted that the inhibitory manner of catechins was non-competitive, whereas that of lignans was competitive. This suggests that there must be an activity-regulatory site, which accommodates catechins specifically but not lignans, other than the active site which accommodates lignans specifically but not catechins. Catechins and lignans must be suitable pr...

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