Differential expression of DAHP synthase and chorismate mutase in various organs of Brassica juncea and the effect of external factors on enzyme activity

The multibranched shikimic acid pathway was discovered as the biosynthetic route to the aromatic amino acids phenylalanine, tyrosine and tryptophan an d a host of other secondary metabolites, An extensive body of work is avail able on the characterization of various enzymes of this pathway in order to understand the underlying mechanisms of aromatic amino acid biosynthesis a nd secondary metabolism in higher plants. In the present investigation, sel ective assays, based on feedback regulation patterns and divalent cation re quirements, mere used to monitor the isozyme profiles of two of the key reg ulatory enzymes of this pathway. 3-Deoxy-D-arabino heptulosonate-7-phosphat e synthase (DAHP synthase/DS) (EC 4.1.2.15) and chorismate mutase (CM) (EC 5.4.99.4) have been characterized from different vegetative and reproductiv e organs of Brassica juncea cv, Pusa Bold, An attempt has also been made to investigate the effect of external factors, such as light and wounding on the regulation of these enzymes. The results reveal differential expression of DAHP synthase and CM in various organs of Brassica and an adaptability of plants to various stresses by up or down regulation of these enzymes.