Some novel features of glutathione transferase from juvenile catfish (Clarias gariepinus) exposed to lindane-contaminated water

Abstract

Catfish are hardy in nature and it is not known whether the presence of efficient detoxication enzymes is partly responsible for this trait. To investigate this, we have assessed induction of glutathione transferase (GST) in 10-week-old juvenile catfish (Clarias gariepinus) exposed to graded concentrations of lindane, an organochlorine insecticide, and characterised the purified enzyme from groups having the highest and statistically significant induction. Some of the unique properties observed for the purified enzyme are a high K m (1.7270.21 mM) for the electrophilic model substrate, 1-chloro-2,4-dinitrobenzene (CDNB) and a very low catalytic rate (V max =0.13070.010 units/mg protein). The k cat /K m being 55.470.2 M À 1 s À 1 . The enzyme is present in high concentration in the organism, the main isoform accounts for about 5.6% of the total soluble protein, probably to compensate for the observed kinetic imperfection. Since these properties are generally not known for a detoxication enzyme, we suggest that they may form part of the organism's own adaptation to its polluted environment.

Effect of Humic Substances as Feed Additive on the Growth Performance, Antioxidant Status, and Health Condition of African Catfish (Clarias gariepinus, Burchell 1822)

“…It is responsible for protection not only against ROS and reactive nitrogen species (RNS), but also for detoxification of an organism [ 48 , 49 ]. The oxidative stress and xenobiotics present in aquatic environment may suppress GSH levels due to the impairment of adaptive mechanisms in fish [ 50 , 51 , 52 ]. For instance, a decrease in GSH levels can be associated with certain pathologies in both humans and animals [ 49 ], while the ratio of glutathione (GSH/GSSG) may characterize the redox and health status of organisms [ 48 ].…”