Detoxifying enzymes, activity

In atherosclerosis and other heart diseases, the role of carotenoids as antioxidants is probable, but for these types of diseases and also for other degenerative diseases such as cancers, non-antioxidant activities constitute other possible prevention mechanisms. These activities are, for example, stimulation of gap junction communications between cells, and the induction of detoxifying enzymes. The... 

Nevertheless, the growing database for aquatic life indicates a number of generalizations (1) many PAHs are acutely toxic at concentrations between 50 and 1000 pg/L (2) deleterious sublethal responses are sometimes observed at concentrations in the range of 0.1 to 5.0 pg/L (3) uptake can be substantial, but depuration is usually rapid except in some species of invertebrates and (4) whole-body burdens in excess of 300 pg benzo[a]pyrene/kg (and presumably other PAHs) in certain teleosts would be accompanied by a rise in the activity of detoxifying enzymes. 

Some of these problems can be overcome by the use of cell-based systems, in particular, primary hepatocytes. Hepatocytes closely simulate the metabolic systems found in the intact fiver and do not require additional cofactors for optimal enzyme activity. However, apart from greater technical difficulties in obtaining hepatocytes as opposed to S9 fraction, hepatocytes can effectively detoxify particular carcinogens and prevent their detection as mutagens. Despite these difficulties, hepatocytes have a role to play in mutagenicity screening, in both bacterial and mammalian-based systems (Tweats and Gatehouse, 1988). 

Laluente MT, Sala JM, Zacarias L (2004) Active oxygen detoxifying enzymes and phenylalanine ammonia-lyase in the ethylene-induced chilling tolerance in citrus fmit. J Agric Food Chem 52(11) 3606-3611... 

Quinone reductase induction. Acetonitrile extract of the dried root, in cell culture at a concentration of 7.9 mg/g, was active on Hematoma-Mouse-lClC7. The sample was assayed for the induction of detoxifying enzymes that may have anticarcinogenic activity . 

The occurrence of a tomatine-detoxifying enzyme in F. solani, was studied in liquid medium with or without tomatine. No tomatinase activity was detected in the absence of tomatine, whereas a remarkable increase of tomatinase activity was observed after 12 h of growth in the presence of the glycoalkaloid, the maximal tomatinase activity being observed after 72 h of incubation [37]. Detection of tomatinase activity in F. solani contrasts with the results reported by Defago and Kern [70],... 

Little information about the mechanism of action of flavonoids is anticipated from in vivo studies. The mechanism of catechin and morin seems to be related to an increase of the activity of detoxifying enzymes like glutathione-S-transferase and NADPH quinone reductase [198, 211]. Similarly, EGCG effect at the colonic level is associated to an increase in tissue superoxide dismutase levels, suggesting that it may act through a potentiation of the antioxidative defense [210]. 

In compartmentation systems (or precursor activation systems), precursors and activating enzymes work synergistically to exert plant defense however, other kinds of synergism were observed. For example, chemicals that enhance the toxicity of furanocoumarin by inhibiting detoxifying enzyme of insects (i.e., cytochrome P-450 monooxygenase) coexist with furanocoumarin in plants.5... 

The challenge here is to find suitable inhibitors at the enzyme level that retain this activity at the whole-plant level. In addition, this approach is only feasible when resistance is conferred by target site mutations if resistance were conferred also by metabolic detoxification an additional set of screens against detoxifying enzymes would have to be included. 

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