Purification and characterization of betacyanoalanine synthase from Pseudomonas straminea

Abstract

Beta-cyanoalanine synthase (EC 4.4.1.9) is a cyanide detoxifying enzyme obtained from Pseudomonas straminea isolated from the effluents of Iron and Steel Smelting Company in Ile-Ife, Osun State. The effluent water samples were screened for their ability to detoxify cyanide and isolates obtained were then screened for b-cyanoalanine synthase production. The samples were screened for their ability to detoxify cyanide and isolates obtained were then screened for β-Cyanoalanine Synthase production. The enzyme was purified through Lyophilization, ion exchange chromatography on CM-Sephadex c-25 and Gel filtration on Biogel P-100. The enzyme had a specific activity of 273.75 U/mg with a purification fold of 2.41 and a yield of 28.90. The native molecular weight of the enzyme was estimated as 54.9 KDa and subunit molecular weight of 60.3 KDa. The Km values of the enzyme for sodium cyanide and L-Cysteine were 8.33 ± 0.05 mM and 1.25 ± 0.26 mM respectively while their maximum reaction velocities were 14.705 ± 0.32 MU/ml/min and 0.1 ± 2.48 MU/ml/min respectively. The optimum temperature and pH for activity were determined to be 40 ^oC and 9.0. The metals tested at the different concentrations of 1 mM, 5 mM and 10 mM enhanced the activity of the enzyme. Inhibition studies on β-Cyanoalanine Synthase Pseudomonas straminea showed that the activity of the enzyme was affected by mercuric chloride, glycine, EDTA and iodoacetamide. The study concluded that β-Cyanoalanine Synthase from Pseudomonas straminea may possess potential bioremediation properties for detoxification of cyanide polluted wastewaters.

Keywords: Beta-cyanoalanine synthase, Hydrogen cyanide, Bacterium, Pseudomonas straminea.