Studies on the biosynthesis of β-n-oxalyl-l-α,β-diaminopropionic acid, the Lathyrus sativus neurotoxin

Abstract

The biosynthesis of β-N-oxalyl-l-α,β-diaminopropionic acid (ODAP), HOOC·CO·NH·CH₂·CH(NH₂·COOH is of interest, since this neurotoxin has been isolated from the seeds of Lathyrus sativus, the consumption of which causes the disease neurolathyrism in humans. The concentration of this non-protein amino acid in the seeds increases on germination. When the seeds are germinated in the presence of [¹⁴C₂]- oxalic acid, the isolated ODAP is labelled exclusively in the oxalyl moiety. An oxalyl- CoA synthetase requiring the obligatory presence of ATP, CoA and Mg²⁺ can be demonstrated in crude extracts of the seedlings. When l-α,β-diaminopropionic acid is incubated with the enzyme in the presence of the components for oxalyl activation, net formation of ODAP can be shown. The enzymic reaction is specific to the β-amino group of l-α,β-diaminopropionic acidm and the higher homologues like α,γ-diaminobutyric acid, ornithine and lysine are inactive in this system. ODAP is not formed with α,β-diaminopropionic acid when the enzyme extract is prepared from Pisum sativum although oxalyl-CoA formation can be demonstrated.