Alternate substrates and inhibitors of 1-aminocyclopropane-1-carboxylic acid synthase

Structural analogs of (−)- S -adenosyl- l -methionine (SAM), in which the heterocyclic base was modified, were used to initiate studies to elucidate the active site conformation of the enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, which was partially purified from Lycopersicon esculentum (tomato). These potential substrate analogs were screened for activity both as substrates and/or as inhibitors of ACC synthase. In general, ACC synthase was found to have a rather rigid specificity for the structural features of the natural substrate (SAM) in that only the purine base adenosine and adenosine analogs in which the N 6 nitrogen was modified were substrates.