Rat Brain Acetyl Cholinesterase as a Biomarker of Cadmium Induced Neurotoxicity

Cadmium as potential environmental xenobiotics has been shown to cross blood brain barrier and to adversely influence the activity of AChE and hence the brain functions. In the present study, we have evaluated the impact of cadmium in vitro on the properties of AChE isolated from rat brain. The enzyme was found to be membrane bound and it could be successfully solubilized using 0.2% (v/v) Triton X-100, a nonionic detergent, in the extraction buffer (50mM Phosphate, pH 7.4). The enzyme was found to be highly stable up to one month when stored at -20°C. This enzyme exhibited maximum activity at pH 7.4. AChE when incubated at different temperatures for 5 min, displayed maximum activity at 37°C. Treatment with higher temperatures caused inactivation of enzyme activity. The enzyme followed a simple Michaelis-Menten curve when assayed at varying substrate concentration and yielded Km value to be 0.0370 mM. When a fixed activity of AChE was assayed in presence of different concentrations of cadmium, the enzyme activity was sharply reduced; the IC50 value being about 5.7mM. The enzyme when assayed in presence of cadmium at a concentration equal to its IC50, lost its 50% activity in 77 min (t1/2). Cadmium was found to act as a noncompetitive inhibitor to the enzyme. These results suggested that AChE from rat brain may serve as a significant biomarker of cadmium induced neurotoxicity..