N.I. Fadzil1, S.A.Ahmad1*,
N.A. Yasid1, M.K.
H.M. Daud3, A. Khalid4,
S.N. Padrilah1 and M.Y.
Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, Universiti
Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
2Faculty of Science
and Natural Resources, Universiti Malaysia Sabah, Jalan UMS, 88400, Kota
Kinabalu, Sabah, Malaysia
Veterinary Laboratory Diagnostic, Faculty of Veterinary Medicine, Universiti Putra
Malaysia, 43400 UPM Serdang, Selangor, Malaysia
4Faculty of Health
Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300
Kuala Lumpur, Malaysia
Author Email :
(ChE) inhibition and histopathological features of brain tissues of Clarias
gariepinus were investigated with a purpose to develop biomarkers for
monitoring heavy metals.
Methodology: The effects of
cadmium toxicity on C. gariepinus were assessed by ChE inhibition and
characterisation of ChE by affinity chromatography and histological
variations in brain tissues were studied by H&E staining under light
Results: The purified
enzyme gave 10.58 fold purification with the recovery of 12% with specific
activity of 159.729 U mg-1. The Michaelis-Menten constant (Km)
and Vmax value obtained was 1.985 mM and 0.4479 µmol min-1
mg-1, respectively. The enzyme showed the ability to hydrolyse
acetylthiocholine iodide (ATC) at a faster rate compared to other two
synthetic substrates, propionylcholine iodide (PTC) and butyrylthiocholine
iodide (BTC). ChE showed highest activity at 35°C in Tris-HCl pH
7.5. The metal inhibition study also found the maximal inhibitory
concentration (IC50) value for cadmium to be 0.6517 mg l-1.
Histological study revealed decrease in the number of cells, degeneration of
Purkinje cells, increased aggregation area and cells necrosis.
Interpretation: Inhibition of
cholinesterase activity and degeneration of Purkinje cells observed in the
present study can be used as a tool for further developing a biomarker for
detecting heavy metals in the aquatic ecosystems.
Key words: Biomarker, Cadmium, Cholinesterase, Clarias gariepinus,