β-N-Oxalyl-L-α,β-diaminopropionic Acid (β-ODAP) Content in Lathyrus sativus: The Integration of Nitrogen and Sulfur Metabolism through β-Cyanoalanine Synthase

Grass pea (Lathyrus sativus L.) is an important legume crop grown mainly in South Asia and Sub-Saharan Africa. This underutilized legume can withstand harsh environmental conditions including drought and flooding. During drought-induced famines, this protein-rich legume serves as a food source for poor farmers when other crops fail under harsh environmental conditions; however, its use is limited because of the presence of an endogenous neurotoxic nonprotein amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (beta-ODAP). Long-term consumption of Lathyrus and beta-ODAP is linked to lathyrism, which is a degenerative motor neuron syndrome. Pharmacological studies indicate that nutritional deficiencies in methionine and cysteine may aggravate the neurotoxicity of beta-ODAP. The biosynthetic pathway leading to the production of beta-ODAP is poorly understood, but is linked to sulfur metabolism. To date, only a limited number of studies have been conducted in grass pea on the sulfur assimilatory enzymes and how these enzymes regulate the biosynthesis of beta-ODAP. Here, we review the current knowledge on the role of sulfur metabolism in grass pea and its contribution to beta-ODAP biosynthesis. Unraveling the fundamental steps and regulation of beta-ODAP biosynthesis in grass pea will be vital for the development of improved varieties of this underutilized legume.