Purification and characterization of a nitrilase from Brassica napus

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Abstract
In germinating seedlings of Brassica napus glucosinolate levels decrease and are potentially degraded to nitriles by a myrosinase. Little is known about the metabolism of glucosinolate aglycone products and the objective of this work was to investigate nitrilase activity and carry out a purification of the enzyme from seedlings of B. napus. A nitrilase capable of converting phenylpropionitrile to phenylpropionic acid was purified to apparent homogeneity from seedlings of B. napus. The protein has a molecular mass of approximately 420 kDa made up of 38 kDa subunits. The pI of the native protein was found to be 4.6. Under denaturing conditions on an isoelectric focusing (IEF) gel a major and minor protein was observed with pI in the range of 5.4‐5.9, suggesting the presence of isoforms. Apart from the potential role of the nitrilase in indole‐3‐acetic acid (IAA) synthesis a developmental study with seedlings indicates that the increase in activity observed may be linked to the in vivo degradation of glucosinolates.