Purification and characterization of nitrile hydratase of mutant 4D of Rhodococcus rhodochrous PA-34

Nitrile hydratase (NHase; E.C. 4.2.1.84) has been purified and characterized using ammonium sulfate precipitation, ion exchange chromatography and gel filtration chromatography from the mutant 4D of Rhodococcus rhodochrous PA-34. The SDS-PAGE and MALDI-TOF analysis of the purified enzyme revealed that it is dimmer consisting of α- and β-subunits with a molecular mass of 25 and 30 kDa, respectively. The K(m) and V(max) values were 102 mM and 350.8 μmol/min/mg using 3-cyanopyridine as substrate. The purified NHase was stable in higher concentration of potassium ions and in acidic pH 5.5 as compared to NHase of the wild R. rhodochrous PA-34. The analysis of the N-terminal amino acid sequence of this enzyme revealed that this enzyme has 90 % homology with the high molecular weight nitrile hydratase of R. rhodochrous J1.