Beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (L-ODAP) toxicity has been associated with lathyrism; a spastic paraparesis caused by excessive dietary intake of the pulse Lathyrus sativus. We investigated the effect of Lathyrus neurotoxin L-ODAP on protein kinase C (PKC) activity under in vitro conditions. L-ODAP activated phosphorylation activity of purified chick brain PKC. Both lysine-rich (histone III-S) and arginine-rich (protamine sulfate) substrate phosphorylation was enhanced in the presence of L-ODAP. The activation is concentration dependent, and maximal activation is observed at 100 microM concentration. Protamine sulfate phosphorylation was enhanced by 47%, whereas histone III-S phosphorylation was enhanced by 50% over PS/PDBu/Ca2+ dependent activity. The nontoxic D-isomer (D-ODAP) did not affect both histone III-S and protamine sulfate phosphorylation activity. These results indicate that L-ODAP taken up by neuronal cells could also contribute to PKC activation and so be associated with toxicity.

Photoproduction of hydrogen by Rhodopseudomonas palustris KU003 under different cultural conditions with various carbon and nitrogen sources was investigated. Hydrogen production was measured using a Gas chromatograph. Malate promoted more amounts of hydrogen production under anaerobic light conditions than anaerobic dark conditions. Cumulative hydrogen production by the organism was recorded at various time intervals. Incubation period of 120 hrs was optimum for production of hydrogen. pH 7.0 ± 0.4 was optimum for production of hydrogen. L-glutamic acid was a good nitrogen source for production of hydrogen. Growing cells produced more amount of hydrogen than resting cells. Significance of the above results in presence of existing literature is discussed.

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Species differences in susceptibility are a unique feature associated with the neurotoxicity of β‐N‐oxalyl‐l‐α,β‐diaminopropionic acid (l‐ODAP), the Lathyrus sativus neurotoxin, and the excitotoxic mechanism proposed for its mechanism of toxicity does not account for this feature. The present study examines whether neurotoxicity of l‐ODAP is the result of an interference in the metabolism of any amino acid and if it could form the basis to explain the species differences in susceptibility. Thus, Wistar rats and BALB/c (white) mice, which are normally resistant to l‐ODAP, became susceptible to it following pretreatment with tyrosine (or phenylalanine), exhibiting typical neurotoxic symptoms. C57BL/6J (black) mice were, however, normally susceptible to l‐ODAP without any pretreatment with tyrosine. Among the various enzymes associated with tyrosine metabolism examined, the activity of only tyrosine aminotransferase (TAT) was inhibited specifically by l‐ODAP. The inhibition was noncompetitive with respect to tyrosine (Ki = 2.0 ± 0.1 mM) and uncompetitive with respect to α‐ketoglutarate (Ki = 8.4 ± 1.5 mM). The inhibition of TAT was also reflected in a marked decrease in the rate of oxidation of tyrosine by liver slices, an increase in tyrosine levels of liver, and also a twofold increase in the dopa and dopamine contents of brain in l‐ODAP‐injected black mice. The dopa and dopamine contents in the brain of only l‐ODAP‐injected white mice did not show any change, whereas levels of these compounds were much higher in tyrosine‐pretreated animals. Also, the radioactivity associated with tyrosine, dopa, and dopamine arising from [14C]tyrosine was twofold higher in both liver and brain of l‐ODAP‐treated black mice. Thus, a transient increase in tyrosine levels following the inhibition of hepatic TAT by l‐ODAP and its increased availability for the enhanced synthesis of dopa and dopamine and other likely metabolites (toxic?) resulting therefrom could be the mechanism of neurotoxicity and may even underlie the species differences in susceptibility to this neurotoxin.

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