This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Secondary Metabolites Degradation → Nitrogen Containing Secondary Compounds Degradation|
Expected Taxonomic Range: Fabaceae
Canavanine, an arginine analog, accumulates in many leguminous plants as a nitrogen storage compound and an antimetabolite involved in plant defense. Arginase catalyzes the first step of canavanine degradation. The reaction releases the stored nitrogen as urea which is further degraded to ammonia by urease. Canaline is a byproduct of the arginase reaction. Canaline is toxic and does not accumulate in plants. The toxicity of canaline comes from its ability to form stable oximes with the carbonyl group of aldehydes and acids and thus depletes TCA cycle compounds. In addition, the formation of canaline-pyridoxal phosphate oxime with pyridoxal phosphate inhibits pyridoxal phosphate-containing enzymes. Canaline is irreversibly converted by canaline reductase which releases homoserine and ammonia. The carbon skeleton released in the form of homoserine supports the biosynthesis of other protein amino acids. In addition, canaline can also be detoxified to canaline-glyoxylate oxime or 3-oxoproprionate (reviewed in [Rosenthal90]).
The jack bean canaline reductase is a novel enzyme which is the only known enzyme to use NADPH to cleave an O-N bond [Rosenthal92].
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