The biosynthesis of β-N-oxalyl-L-α,β-diaminopropionic acid (ODAP) the Lathyrus sativus neurotoxin has been found to follow the scheme depicted below: Mg²⁺ Oxalate + ATP + Coenzyme A → Oxalyl-CoA + AMP + PPi Oxalyl-CoA + L-α,β-diaminopropionic acid → ODAP + CoA. The first reaction is catalysed by oxalyl-CoA synthetase which has properties similar to that of the enzyme in peas. The second reaction is catalysed by another enzyme which is specific to L. sativus and is designated as oxalyl-CoA-α,β-diaminopropionic acid oxalyl transferase. The enzymes have been purified by about 60-fold and their properties studied. A partial resolution of the two enzyme activities has been achieved using CM-sephadex columns.