-Canaline ( IUPAC name 2-amino-4-(aminooxy)butyric acid)) is a non-

proteinogenic amino acid Proteinogenic amino acids are amino acids that are incorporated biosynthetically into proteins during translation. The word "proteinogenic" means "protein creating". Throughout known life, there are 22 genetically encoded (proteinogenic) amino aci ...

. The compound is found in

legumes A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock fo ...

that contain

canavanine L-(+)-(''S'')-Canavanine is a non-proteinogenic amino acid found in certain leguminous plants. It is structurally related to the proteinogenic α-amino acid L-arginine, the sole difference being the replacement of a methylene bridge (-- unit) in ...

, from which it is produced by the action of

arginase Arginase (, ''arginine amidinase'', ''canavanase'', ''L-arginase'', ''arginine transamidinase'') is a manganese-containing enzyme. The reaction catalyzed by this enzyme is: : arginine + H2O → ornithine + urea It is the final enzyme of the ure ...

. The most common-used source for this amino acid is the jack bean, '' Canavalia ensiformis''.

Toxicity

-Canaline is the only naturally occurring amino acid known that has an ''O''-alkyl

hydroxylamine Hydroxylamine is an inorganic compound with the formula . The material is a white crystalline, hygroscopic compound.Greenwood and Earnshaw. ''Chemistry of the Elements.'' 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431–43 ...

functionality in the side chain. This amino acid is structurally related to

ornithine Ornithine is a non-proteinogenic amino acid that plays a role in the urea cycle. Ornithine is abnormally accumulated in the body in ornithine transcarbamylase deficiency. The radical is ornithyl. Role in urea cycle L-Ornithine is one of the prod ...

(it is the 5-oxa derivative) and is a potent insecticide. Tobacco hornworm larvae fed a diet containing 2.5 mM canaline showed massive developmental aberrations, and most larvae so treated died at the pupal stage. It also exhibits potent neurotoxic effects in the moth. PDB 1oat EBI

Its toxicity stems primarily from the fact that it readily forms oximes with keto acids and aldehydes, especially the

pyridoxal phosphate Pyridoxal phosphate (PLP, pyridoxal 5'- phosphate, P5P), the active form of vitamin B6, is a coenzyme in a variety of enzymatic reactions. The International Union of Biochemistry and Molecular Biology has catalogued more than 140 PLP-depende ...

cofactor of many vitamin B₆-dependent enzymes. It inhibits

ornithine aminotransferase Ornithine aminotransferase (OAT) is an enzyme which is encoded in human by the OAT gene located on chromosome 10. The OAT involved in the ultimate formation of the non-essential amino acid proline from the amino acid ornithine. Ornithine amin ...

at concentrations as low as 10 nM.

Plant nutrition

-Canaline is a substrate for

resulting in the synthesis of -ureidohomoserine (the corresponding analog of -citrulline). In turn, the latter forms -canavaninosuccinic acid in a reaction mediated by argininosuccinic acid synthetase. -Canavaninosuccinic acid is cleaved to form -canavanine by argininosuccinic acid synthetase. By these sequential reactions, the canaline-urea cycle (analogous to the ornithine-urea cycle) is formed. Every time a canavanine molecule runs through the canaline-urea cycle, the two terminal nitrogen atoms are released as urea. Urea is an important by-product of this reaction sequence because it makes ammonicial ammonia (urease-mediated) that is available to support intermediary nitrogen metabolism. -Canaline can be reductively cleaved to - homoserine, a non-protein amino acid of great importance in the formation of a host of essential amino acids. In this way, the third nitrogen atom of canavanine enters into the reactions of nitrogen metabolism of the plant. As homoserine, its carbon skeleton also finds an important use.

References

*{{pn, date=February 2015 Amino acids Toxic amino acids Non-proteinogenic amino acids