1-aminocyclopropanecarboxylic acid (ACPC) is a non-proteinogenic alpha-amino acid consisting of cyclopropane having amino and carboxy substituents both at the 1-position. It has a role as a plant metabolite and a member of ethylene releasers. ACPC is produced endogenously in the tomato and other higher plants as a product of the action of 1-aminocyclopropane-1-carboxylic acid synthase in the biosynthesis of ethylene. It is a monocarboxylic acid and a non-proteinogenic alpha-amino acid. It derives from a cyclopropanecarboxylic acid. ACPC is a partial agonist at the strychnine-insensitive glycine recognition site on the N-methyl-D-aspartate (NMDA) receptor complex in the mammalian central nervous system with preclinical activity in animal models of neuroprotection and psychiatric illnesses. Half-maximal activation by ACPC as a glycine-site agonist was 0.7 to 0.9 microM. Half-maximal inhibition by ACPC was dependent on NMDA concentration. Peak responses to a >100 microM ACPC pulse in the presence of 1 microM glutamate were similar to those of glycine but decayed to a steady-state amplitude below that of glycine. The removal of ACPC initially caused an increase in inward current followed by a subsequent decrease to baseline levels. This suggests that relief of low-affinity antagonism occurs before high-affinity agonist dissociation. ACPC is shown to block convulsions and death produced by NMDA exposure, significantly reducing seizure induction and cell death of NMDA-treated hippocampal neurons.