Definition
ChEBI: 3-cyanoalanine is an alanine derivative obtained by replacement of one of the methyl hydrogens in alanine with a cyano group It is an alanine derivative, an aliphatic nitrile and a non-proteinogenic alpha-amino acid.
Metabolism
In the living plant, 3-cyanoalanine is mainly bound as its gama-glutamyl derivative. The enzyme, beta-cyanoalanine synthase, catalysing the reaction between cysteine and cyanide has been isolated from seedlings of the blue lupin (Lupinus angustifolius, Leguminosae).
3-Cyanoalanine is a neurotoxin, causing convulsions and muscular rigidity in rats and chicks. In rats, the compound also causes cystathioninuria, the lethai dose being 20mg/100g body weight. This metabolic defect can be prevented by injection of pyridoxal phosphate. Thus, beta-cyanoalanine interferes with pyridoxal metabolism and inhibits the enzyme gama-cystathionase.
In non-accumulating plants, 3-cyanoalanine is enzymatically hydrolysed to the protein amino acid, asparagine, by 3-cyanoalanine hydrolase. Thus, this nonprotein amino acid could be a ubiquitous constituent of plants, but may only accumulate in those species whieh do not contain 3-cyanoalanine hydrolase.
