Monoclonal antibodies against apple 1-aminocyclopropane-l-carboxylate synthase

Abstract

1-Aminocyclopropane-l-carboxylate (ACC) synthase from apple fruits was purified over 5,000-fold by conventional column chromatography. By immunizing mice with this partially purified enzyme preparation, 8 hybridoma lines producing monoclonal antibodies against apple ACC synthase were isolated. While all 8 clones immunoprecipitated native ACC synthase, only two clones recognized the putative (48 kDa) ACC synthase on Western blots. When a partially purified ACC synthase preparation was incubated with S-adenosyl-L-[carboxyl- 14C]methionine (AdoMet), only one radioactive protein of 48 kDa was detected on sodium dodecyl sulfate-poly-acrylamide gel electrophoresis. This radioactive protein was specifically immunoprecipitated by the monoclonal antibodies, indicating that apple ACC synthase is specifically radiolabeled by its substrate AdoMet, as is tomato ACC synthase. Thus, the monoclonal antibodies recognized both native and AdoMet-inactivated forms of ACC synthase. While these antibodies failed to im-munoprecipitate ACC synthase isolated from ripe tomato fruits, ripe avocado fruits or auxin-treated mungbean hypocotyls, they were effective in immunoprecipitating the enzyme isolated from ripe pear fruits. © 1991 The Japanese Society of Plant Physilogists(JSPP).