Nitrilase activity in clubroot diseased plants

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Abstract
Nitrilase activity was detected in desalted extracts of leaves, hypocotyls and roots of swede (Brassica napus) but was considerably higher in leaves than in roots. After inoculation with Plasmodiophora brassicae infected roots and hypocotyls showed an increase in nitrilase activity beginning at the early stages of club development before total protein increased significantly. Enzyme activity of infected tissue was partially purified by DEAE ion exchange chromatography and compared to the enzyme extracted from non infected seedlings. It appears that the increase in nitrilase activity is due to an increase of the plant enzyme which is initially present with lower activity. Km values for the artificial substrate 3‐cyanopyridine and for indole‐3‐acetonitrile were 2.1 × 10−3 M and 6.2 × 10−4M, respectively. The role of nitrilase activity for IAA biosynthesis is discussed.