Canaline
Encyclopedia
L-Canaline) is a non-protein amino acid. The compound is found in legumes that contain [canavanine], from which it is produced by the action of arginase
. The most common-used source for this amino acid is the jack bean, Canavalia ensiformis
. It is grown commercially as a source of the enzyme-urease.
L-Canaline is the only naturally occurring amino acid known that has an O-alkyl hydroxylamine
functionality in the side chain. This amino acid is structurally related to ornithine
(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.
Its toxicity stems primarily from the fact that it readily forms oximes with keto acids and aldehydes, especially the pyridoxal phosphate cofactor of many Vitamin B6-dependent enzymes. It inhibits ornithine aminotransferase
at concentrations as low as 10 nM.
L-Canaline is a substrate for ornithine aminotransferase resulting in the synthesis of L-ureidohomoserine (the corresponding analog of L-citrulline). In turn, the latter forms L-canavaninosuccinic acid in a reaction mediated by argininosuccinic acid synthetase. L-Canavaninosuccinic acid is cleaved to form L-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. L-Canaline can by reductively cleaved to L-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.
Arginase
Arginase is a manganese-containing enzyme. The reaction catalyzed by this enzyme is: arginine + H2O → ornithine + urea. It is the final enzyme of the urea cycle.- Structure and function :Arginase belong to the ureohydrolase family of enzymes....
. The most common-used source for this amino acid is the jack bean, Canavalia ensiformis
Canavalia ensiformis
Canavalia ensiformis, or Jack-bean, is a legume which is used for animal fodder and human nutrition, especially in Brazil where it is called feijão-de-porco . It is also the source of concanavalin A.- Description :...
. It is grown commercially as a source of the enzyme-urease.
L-Canaline is the only naturally occurring amino acid known that has an O-alkyl hydroxylamine
Hydroxylamine
Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...
functionality in the side chain. This amino acid is structurally related to ornithine
Ornithine
Ornithine is an amino acid that plays a role in the urea cycle.-Role in urea cycle:L-Ornithine is one of the products of the action of the enzyme arginase on L-arginine, creating urea. Therefore, ornithine is a central part of the urea cycle, which allows for the disposal of excess nitrogen....
(it is the 5-oxa derivative) and is a potent insecticide. Tobacco hornworm
Tobacco hornworm
Manduca sexta is a moth of the family Sphingidae present through much of the American continent. Commonly known as the tobacco hornworm, it is closely related to and often confused with the very similar tomato hornworm ; the larvae of both feed on the foliage of various plants from the family...
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.
Its toxicity stems primarily from the fact that it readily forms oximes with keto acids and aldehydes, especially the pyridoxal phosphate cofactor of many Vitamin B6-dependent enzymes. It inhibits ornithine aminotransferase
Ornithine aminotransferase
Ornithine aminotransferase is an enzyme involved in the ultimate formation of proline from ornithine. Ornithine aminotransferase forms the initial intermediate in this process. It catalyzes the reverse reaction as well, and is therefore essential in creating ornithine from the starting substrate...
at concentrations as low as 10 nM.
L-Canaline is a substrate for ornithine aminotransferase resulting in the synthesis of L-ureidohomoserine (the corresponding analog of L-citrulline). In turn, the latter forms L-canavaninosuccinic acid in a reaction mediated by argininosuccinic acid synthetase. L-Canavaninosuccinic acid is cleaved to form L-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. L-Canaline can by reductively cleaved to L-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.