We report the properties of partially purified rhodanese, a cyanide detoxifying enzyme isolated from the kidney of the greater cane rat commonly known as grasscutter (Thryonomys swinderianus). T. swinderianus kidney rhodanese had a specific activity of 1.43 µmole/min/mg protein, a fold of 2.31 and a 55% recovery. The apparent Km values of 0.408 and 0.316 mM were obtained for both sodium thiosulphate (Na2S2O3) and potassium cyanide (KCN) respectively. Substrate specificity study showed that T. swinderianus rhodanese can use other substrates. The enzyme showed its maximum activity at pH 8.0 and 50°C. The assay for the effect of metal ions showed that the enzyme is not affected or inhibited by metal ions such as Na+, Fe3+ but inhibited by Hg2+. The continued existence of T. swinderianus after consumption of food crops with high cyanogenic glycosides suggests that the animal has a functional cyanide detoxification mechanism.
Keywords: Rhodanese, cyanide, kinetics, detoxification, cane rat, grasscutter.
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