A selective assay for prephenate aminotransferase activity in suspension-cultured cells of Nicotiana silvestris.

Prephenate aminotransferase in Nicotiana silvestris Speg. et Comes is highly stable to thermal treatment. This property was exploited to obtain, by treatment at 70° C for 10 min, a residual level (1-4%) of aspartate aminotransferase activity that proved to be catalyzed exclusively by prephenate aminotransferase. The latter enzyme was the most mobile of all aspartate aminotransferase bands during polyacrylamide-gel electrophoresis conducted under non-denaturing conditions. This methodology for convenient assay of prephenate aminotransferase in crude extracts, as demonstrated for N. silvestris, may generally apply to higher plants since prephenate aminotransferase from a variety of plant sources has been found to exhibit high thermal stability.