{'fraction_non_alphanumeric': 0.028985507246376812, 'fraction_numerical': 0.025987006496751622, 'mean_word_length': 4.6875, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Biochemical characterisation of purified acetylcholine esterase from liver of Tilapia (Tilapia zilli)

Acetylcholinesterase (AChE) is suitable for monitoring the occurrence of pesticide classes in the environment. Although this enzyme have been characterized from different species of fishes with focus on the head tissue (brain) due to the activity of acetylcholine esterase in relation to neurotransmission. However, the presence of this enzyme in significant concentration in other tissue other than that of the nervous system and muscles is under reported. Here we report the purification of AChE from the liver of Tilapia zilli by ion-exchange chromatography on DEAE-sephadex A50 and gel filtration on Sephadex G-100. At the same time the biochemical characterization and kinetic parameters of this enzyme were determined. Two distinct forms of AChE were determined from the purification experiment and were denoted as AChE A* and AChE B* . A 26.25-fold purification with a recovery of 21.32% was achieved for AChE A* and AChE B* had 39.44-fold purification with 15.60% activity recovered. Furthermore, the subunit molecular weights of AChE A* and AChE B* were 42.4 and 38.7 kDa respectively. The two enzymes were optimally active at pH 8.0 and 40 °C. The apparent K m and V max values of AChE A* were 0.5 mM and 25.1 mM/min respectively while the apparent K m and V max values of AChE B* were 0.31 mM and 15.7 mM/min respectively. The activity of the enzymes was inhibited by cypermethrin, chlorpyrifos, and dichlorvos. However, dichlorvos shows a greater inhibition of activities of AChE A* and AChE B* , with IC 50 value of 0.016 and 0.005 μM respectively when compared with that of cypermethrin and chlorpyrifos. The results established the activity of acetylcholine esterase in the liver of Tilapia zilli and our findings shows that there are two possible variants of the enzyme present in the liver and both variant can serve as a possible biomarker for monitoring environmental pollutants.