Ammonium sulfate activation of phosphodiesterase in homogenates of larvae of the European corn borer

Summary European corn borer phosphodiesterase is highly activated by (NH4)2SO4 and moderately activated by NH4Cl (pH 7.6, 33°). Vertebrate and crayfish diesterases, on the other hand, are inhibited by (NH4)2SO4. It is likely that (NH4)2SO4 causes some configurational change in the European corn borer phosphodiesterase molecule which results in the exposure of more active sites and hence greater enzyme activity. In in vitro tests caffeine (0.008 M) and theophylline (0.008 M) inhibit phosphodiesterase more effectively in European corn borer larvae than in crayfish, ovine, bovine, or rat tissue.