Purification and properties of a cyanide-degrading enzyme from Burkholderia cepacia strain C-3

A cyanide-hydrolysing enzyme from Burkholderia cepacia strain C-3 isolated from soil was purified to electrophoretic homogeneity by ammonium sulphate precipitation and column chromatography on HiTrap Q (DEAE-agarose) and phenyl-Sepharose HP. The enzyme was purified 48-fold with a 0.8% yield and a final specific activity of 26.8 u/mg protein. The purified enzyme was observed as a single polypeptide band of molecular mass 38 kDa during both denaturing and non-denaturing gel electrophoresis. Enzymatic activity was optimal at pH 8.0-8.5 and at 30-35 degrees C. Activity was stimulated by Mo2+, Sn2+, and Zn2+, and inhibited by Al3+, Co2+, Cu2+ and Hg2+. The enzyme was specific for cyanide and thiocyanate with formate and ammonia as the main products from KCN degradation. Its K-m and V-max values were 1.4 mM and 15.2 u/mg protein, respectively. Apparent substrate inhibition occurred at cyanide concentrations greater than 2 mM.