Inhibitory Substances of a Tau-Type Pumpkin Glutathione S-Transferase: Their Existence and Chemical Properties

Distributions of physiological inhibitors of a tau-type pumpkin glutathione S-transferase (CmGSTU3) have been investigated in different organs of pumpkin plants, as well as onion bulb and water hyacinth root. Inhibitory effects were observed in alcoholic extracts of all plant parts, but the extracts prepared from the roots of either water hyacinth or pumpkin plant showed the highest effect on CmGSTU3 toward 1-chloro-2,4- dinitrobenzene (CDNB). Results of various chromatographies indicated that a number of inhibitory substances were present in the alcoholic extract of each plant organ. Some macromolecules in the plant extracts exhibited inhibitory effects; however, the extracts might contain a large number of unknown, low-molecular-weight inhibitory substances. Some of the low-molecular-weight inhibitors in water hyacinth root extract showed characteristic fluorescence under UV light