Biochemical Properties of Rhodanese from Almond (Prunus amygdalus) Nuts

Study of the characteristic pattern of enzymes are useful in the understanding of certain physiological and biochemical process-es. Thiosulfate: cyanide sulfurtransferase (rhodanese) is a ubiquitous multifunctional enzyme, that is believed to function in cyanide detoxification. The present study was conducted to determine the activity of rhodanese in almonds (Prunus amygdalus) that belong to the rose family, rosaceae. Rhodanese from the almond nuts was purified by ammonium sulphate precipitation, ion exchange and affinity chromatography. The molecular weight of the enzyme was determined by sodium dodecyl sulphate poly-acrylamide gel electrophoresis. The purified rhodanese from the almond nuts had a specific activity of 5.09 RU/mg with yield of 0.06%. A Km value of 11.14 mM with Vmax 0.46 RU/ml/min were obtained from KCN while a Km value of 13.95 mM with Vmax of 0.48 RU/ml/min was obtained from Na2S2O3. The substrate specificity studied indicated that Mercapto-ethanol (MCPE), Ammonium per sulfate ((NH2)2S2O8, Ammonium sulfate ((NH2)2SO4, Sodium sulfate (Na2SO4) and Sodium metabi-sulfate (Na2S2O5) cannot be substituted for sodium thiosulphate (Na2S2O3) as sulphur donor for rhodanese catalytic reaction. The optimum activity of the enzyme was observed at 50oC and an optimum pH of 8. The effect of metals on rhodanese from Almond nut showed that at 1 mM concentration of the metals used did not pronouncedly affect the activity of the enzyme metals except that of HgCl2 and MnCl2. However, the divalent metals including MnCl2 HgCl2, CaCl2, and BaCl2 inhibited the enzyme at 10 mM concentration. The molecular weight obtained from sodium dodecyl sulphate polyacrylamide gel electrophoresis was estimated to be 35 kDa. The study validates the expression of rhodanese activity in almond nut. The characteristic property of rhodanese in the plant may be exploited for bioremediation of cyanide polluted soil.