Lathyrus sativus (grass pea) and its neurotoxin ODAP

Lathyrus sativus (grass pea) is a high-yielding, drought-resistant legume consumed as a food in Northern India and neighboring countries as well as in Ethiopia. Its development into an important food legume, however, has been hindered by the presence of the neurotoxin - beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (beta-ODAP) in seeds which, if consumed in large quantities for prolonged periods, can cause irreversible paralysis. Recently, some low-toxin lines have been developed that may prove safe for both animal and human foods. Cultivation of L. sativus should thus be considered in suitable regions because the demand for legume animal feed protein products is expected to increase. This paper addresses advances in understanding L. sativus from the perspective of its taxonomy, genetics, ecology, chemistry, nutrition, medicine, biology and for animal nutrition.     

60Coγ射线与EMS复合处理对山黧豆抗氧化酶活力及ODAP含量的影响

Lathyrus sativus seeds were treated with ⁶⁰Coγ-ray and EMS(ethyl methane sulfonate), and their emergence rate and SOD,POD and CAT activities were determined. The result indicated that the treatment decreased the emergence rate. The activities of SOD and POD were changed in accordance with the increase of irradiation dose and EMS concentration, while that of CAT had no obvious change. After treatment, the ODAP content in Lathyrus sativus decreased. Amutant was developed, with toxin content of 0.1%, compared to 0.2% in control.     

山黧豆毒素ODAP的生物合成及与抗逆性关系研究进展

有关山黧豆毒素ODAP的生物合成途径的前体物和合成程序已经证实,但其关键合成酶尚未分离与鉴定,因而无法克隆相应基因和利用反义RNA技术以控制其生物合成。研究表明,利用相应的抑制剂控制ODAP生物合成前体物可降低ODAP的积累量。山黧豆中ODAP含量与其抗逆性之间密切相关,这与其能有效地清除山黧豆中·OH自由基有关,外源ODAP处理获同样效果。此外,因ODAP既是含氮化合物,又是游离氨基酸,极易溶于水,可在逆境胁迫下与脯氨酸和多胺一样大量而迅速地积累,推测它也可能作为细胞渗透调节物质和防脱水剂,并在氮代谢和能量代谢方面起重要作用。对今后该领域的重点研究方向也进行了探讨。     

Receptor Interactions of β-N-Oxalyl-L-α,β-Diaminopropionic Acid,the Lathyrus sativus Putative Excitotoxin,with Synaptic Membranes

Direct evidence for the excitotoxicity of -N-oxalyl-L-,-diaminopropionic acid (ODAP), the Lathyrus sativus neurotoxin has been studied by examining the binding of chemically synthesized [2,3 ³H]ODAP ([³H]ODAP) to synaptic membranes. [³H]ODAP binding to membranes was mostly nonspecific, with only a very low specific binding (15–20% of the total binding) and was also not saturable. The low specific binding of [³H]ODAP remained unaltered under a variety of assay conditions. A low B_max of 3.2 ± 0.4 pmol/mg and K_d 0.2 ± 0.08 M could be discerned for the high affinity interactions under conditions wherein more than 80–90% of the binding was nonspecific. While ODAP could inhibit the binding of [³H]glutamate to chick synaptic membranes with a K_i of 10 ± 0.9 M, even L-DAP, a non neurotoxic amino acid was also equally effective in inhibiting the binding of [³H]glutamate. The very low specific binding of [³H]ODAP to synaptic membranes thus does not warrant considering its interactions at glutamate receptors as a significant event. The results thus suggest that the reported in vitro excitotoxic potential of ODAP may not reflect its true mechanism of neurotoxicity.     

山黧豆毒素的薄层分离

通过对山黧豆中常见的20几种游离氨基酸薄层层析发现,其毒素ODAP的Rf值与好几种相关氨基酸的接近,而用阳离子交换柱对氨基酸抽提样进行简单的分离纯化,第一个洗脱出来的即为ODAP,这样在排除其它氨基酸干扰的情况下再进行ODAP的薄层分析将得到准确的结果。     

水分胁迫下山黧豆中ABA及ODAP的积累研究

用PEG、PEG+ABA、ABA分别处理15d龄的山黧豆幼苗,取其叶片为实验材料,测定内源ABA、ODAP、MDA和H₂O₂含量以及几种抗氧化酶活性,结果表明,与对照相比处理材料叶片中ABA和ODAP含量显著增加;外源ABA的加入降低了PEG胁迫引起的MDA和H₂O₂含量的增加,延缓了PEG胁迫引起的CAT活性的衰减,提高了GR活性.用外源ABA长时间处理山黧豆,发现叶片中ABA含量显著增加,随后出现ODAP的积累;ABA处理初期(0～3d)对叶片中活性氧代谢影响不大,随着ABA处理时间的延长(7～15d),可引起叶片中SOD、POD、CAT、GR活性的降低,MDA、H₂O₂含量的增加,表明ABA确实可促进ODAP的积累.     

β-N-oxalyl-L-α,β-diaminopropionic acid regulates mitogen-activated protein kinase signaling by down-regulation of phosphatidylethanolamine-binding protein 1

β-N-Oxalyl-L-α,β-diaminopropionic acid (l-ODAP) an α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor agonist activates protein kinase C in white leghorn chick brain. The current study focuses on the protein kinase C downstream signaling targets associated with L-ODAP excitotoxicity in SK-N-MC human neuroblastoma cells and white leghorn male chick (Gallus domesticus) brain extracts. L-ODAP treatment in SK-N-MC cells (1.5 mM) and chicks (0.5 mg/g body weight) results in a decreased expression and increased phosphorylation of phosphatidylehthanolamine-binding protein 1 (PEBP1) up to 4 h which however, returns to normal by 8 h. D-ODAP, the non-toxic enantiomer however, did not affect PEBP1 levels in either chick brain or SK-N-MC cells. Decreased PEBP1 expression correlated with subsequent activation of Raf-1, MEK and ERK signaling components of the mitogen-activated protein kinase cascade and nuclear translocation of hypoxia inducible factor-1α (HIF-1α) in chick brain nuclear extracts and SK-N-MC cells. SK-N-MC cells over-expressing PEBP1 inhibited nuclear translocation of HIF-1α when treated with l-ODAP, indicating that down-regulation of PEBP1 is responsible for HIF-1α stabilization and nuclear localization. Excitotoxicity of L-ODAP may thus be the result of phosphorylation and down-regulation of PEBP1, a crucial signaling protein regulating diverse signaling cascades. L-ODAP induced convulsions and seizures in chicks could be the result of a hypoxic insult to brain.     

山黧豆胚胎发育过程中ODAP和一些大分子物质含量的变化

应用微量分析方法检测了山黧豆胚胎发育过程中ODAP毒素含量和核酸、蛋白质、糖类等大分子物质的含量变化。结果表明:每粒种子的ODAP含量随着胚的发育而增加。每粒种子DNA量随着细胞的迅速分裂而增加,R、蛋白质、淀粉含量随着胚的发育而成倍地增加,当进入心形胚时这些物质的增加更为迅速。如以每克干重中的含量来表示,那么ODAP、DNA及可溶性糖含量则随胚的发育而下降,其它大分子物质含量在胚发育前期升高,进入心形胚时,这些物质达到最高峰;到鱼雷胚时,这些物质含量开始下降,直到胚基本分化完全时,降到最低点;只有酸性蛋白质含量一直保持增长。