IMMUNOLOGICAL STUDIES ON L-GLUTAMIC ACID DECARBOXYLASE FROM ESCHERICHIA COLI K-12

The immunological properties of glutamic acid decarboxylase (GAD) from three strains of Escherichia coli K-12 with different levels of enzyme activity were examined. Each strain was grown under conditions where high GAD activity is produced (glucose at 37 ° and succinate at 30 °) and under conditions where low levels of the enzyme are formed (succinate at 37 °). All the nine preparations gave almost identical precipitation curves with anti-GAD serum prepared in rabbits against a purified GAD preparation. A single line of precipitation was obtained by double diffusion in agar with all the nine GAD preparations. No cross reacting material (CRM) was detected in extracts from cultures with low GAD activity. These data strongly support the conclusion that the differences in enzyme activity between the various preparations studied did not result from the production of structurally different enzyme molecules by the different cultures studied. © 1969.