To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

4,5
Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.
.
Leo
Newton
Brights
Milds

From Wikipedia, the free encyclopedia

Canavanine
Chemical structure of L-(+)-(S)-canavanine
Names
Preferred IUPAC name
Canavanine
Systematic IUPAC name
(2S)-2-amino-4-{[(diaminomethylidene)amino]oxy}butanoic acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
DrugBank
ECHA InfoCard 100.153.281 Edit this at Wikidata
EC Number
  • 624-714-2
KEGG
MeSH Canavanine
UNII
  • InChI=1S/C5H12N4O3/c6-3(4(10)11)1-2-12-9-5(7)8/h3H,1-2,6H2,(H,10,11)(H4,7,8,9)/t3-/m0/s1
  • N[C@@H](CCON=C(N)N)C(O)=O
Properties
C5H12N4O3
Molar mass 176.176 g·mol−1
Density 1.61 g·cm−3 (predicted)
Melting point 184 °C (363 °F; 457 K)
Boiling point 366 °C (691 °F; 639 K)
soluble
Solubility insoluble in alcohol, ether, benzene
log P -0.91 (predicted)
Vapor pressure 1.61 μPa (predicted)
Acidity (pKa) 2.35 (carboxylic acid), 7.01 (oxoguanidinium), 9.22 (ammonium)
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H302, H312, H332
Flash point 214.6 °C (418.3 °F; 487.8 K) (predicted)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

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 (-CH
2
- unit) in arginine with an oxa group (i.e., an oxygen atom) in canavanine. Canavanine is accumulated primarily in the seeds of the organisms which produce it, where it serves both as a highly deleterious defensive compound against herbivores (due to cells mistaking it for arginine) and a vital source of nitrogen for the growing embryo.[citation needed] The related L-canaline is similar to ornithine.

YouTube Encyclopedic

  • 1/5
    Views:
    643 631
    350 374
    166 575
    129 489
    998
  • Classification of amino acids | Chemical processes | MCAT | Khan Academy
  • 10 AUTOIMMUNE Conditions Benefit from CARNIVORE Diet (Research) 2023
  • Nutritional Benefits of Sprouts Explained By Dr. Berg
  • Alfalfa Sprouts, Best Quality to Consume for Highest Health Benefits
  • What Happens To Your Body When You Eat Celery Everyday | How to cook

Transcription

All right. So let's go through the classification of amino acids. And I've highlighted the word class within classification for you, because I'm going to paint for you a picture of a classroom that is full of 20 different amino acids. And just picture this as the most diverse classroom you've ever seen, because each amino acid has their own unique side chain, and this makes them distinctly different from the amino acid next to them. And just like a real classroom full of kids, even though each amino acid is unique and special in their own way, you can start to see that some of these amino acids are more alike than they are different. And we can start to see these similarities in the chemical properties of the side chains, and this allows us to group them together into various categories. And those chemical properties include the charge of the side chain, the ability of the side chain to undergo hydrogen bonding, and also whether or not we can classify that side chain as being either acidic or basic. So the 20 amino acids can be split broadly into kind of two main groups. The first group includes the nonpolar amino acids, and then the second group includes the polar ones. And the nonpolar amino acids can also be thought of as the hydrophobic, or water-fearing, amino acids. And conversely, you have the polar ones. Those can be considered hydrophilic, meaning water-loving. And yet another way that I like to kind of think about these two main groups are the hydrophobic amino acids-- they're kind of like the water-haters. They don't really want to interact with water at all. They'd rather just interact with themselves. Whereas the hydrophilic amino acids are very open and welcoming to interacting with water, and so they're water-lovers. And then within the two groups of nonpolar hydrophobic and polar hydrophilic amino acids, you then have a further breakdown into subgroups. And those subgroups include those amino acids that have alkyl side chains, aromatic side chains, neutral ones, acidic ones, or basic ones. So let's take a closer look at those amino acids that have alkyl groups as side chains. And as you can see here, we have seven different amino acids, and I've just drawn out the side chain for you. I've left the rest of the molecule out just to fit everything in here. And we have glycine, alanine, valine, methionine, leucine, isoleucine, and proline. And proline is the exception. I've drawn out the entire amino acid there, because as you can see, its side chain forms this interesting ringed structure with the amino group in the backbone of the molecule. So I just included it there for completeness. So all these side chains are made up of alkyl groups, with the one exception being glycine, because its side chain has only a hydrogen atom in it. But because it behaves similarly to an alkyl chain side group, it gets slumped into this category of amino acids. And whenever you see an amino acid with an alkyl group as its side group, you should be thinking that this amino acid is nonpolar. And so they're also going to be hydrophobic. Now, let's take a closer look at those amino acids that have aromatic groups as part of their side chain, and remember, we're still under the umbrella of nonpolar hydrophobic amino acids here. And so I've drawn out for you here two amino acids, phenylalanine and tryptophan. And what should you be thinking when you're looking at these amino acids? So besides thinking, oh, those amino acids must smell really good, because they're called aromatic amino acids-- well, that might be true, but you should also be thinking the same thing that you think when you see amino acids with alkyl groups as their side chains. These amino acids that you see here are also nonpolar and hydrophobic. And that kind of makes sense, because aromatic chains are also just made up of carbons and hydrogens. And you weren't wrong if you thought that aromatic compounds might smell really good, because many of our most aromatic herbs and spices that we're all familiar with, like basil or cinnamon and vanilla, are composed of the same sorts of ring structures that we see here. All right. So now that we've tackled the nonpolar hydrophobic amino acids, let's dive on into the polar and hydrophilic amino acids. The first group that we will look at is the neutral group. Here we have serine, threonine, asparagine, glutamine, cystine, and tyrosine. The way that I remember that these are the polar amino acids is that these amino acids have a side chain that contain an oxygen or a sulfur atom, which tends to hog all the electrons around them to create a localized negative charge over that atom and then a positive charge over the rest of the side chain. So you can kind of see why these amino acids like to hang out with water now, since water is also polar in the same way. And these amino acids are considered neutral, because although they are polar enough to interact with water, they're not strongly polar enough to qualify as an acid or a base. So which of the polar hydrophilic amino acids do qualify as acidic? Well, that would be these two amino acids here, aspartic acid and glutamic acid. As you can see, these amino acids have a carboxylic acid as part of their side chain, which is a very willing, strong hydrogen donor which qualifies these amino acids as acidic. When these side chains do donate their hydrogen and they're left in anion form, then in that case, we refer to them as aspartate and glutamate, respectively. So you might see them referred to in that way. Last but not least, we have the basic amino acids, and they're histidine, lysine, and arginine. And the way I remember that these amino acids are basic is that if you take a closer look at their side chains, you see a few nitrogen atoms. And remember that nitrogen is a very willing proton accepter, and this is why they qualify as basic.

Toxicity

The mechanism of canavanine's toxicity is that organisms that consume it typically mistakenly incorporate it into their own proteins in place of L-arginine, thereby producing structurally aberrant proteins that may not function properly. Cleavage by arginase also produces canaline, a potent insecticide.

The toxicity of canavanine may be enhanced under conditions of protein starvation,[1] and canavanine toxicity, resulting from consumption of Hedysarum alpinum seeds with a concentration of 1.2% canavanine weight/weight, has been implicated in the death of a malnourished Christopher McCandless.[2] (McCandless was the subject of Jon Krakauer's book (and subsequent movie) Into the Wild).

Side-by-side comparison of the structures of canavanine and arginine, with the difference highlighted
Chemical structure of canavanine compared to arginine

In mammals

NZB/W F1, NZB, and DBA/2 mice fed L-canavanine develop a syndrome similar to systemic lupus erythematosus,[1] while BALB/c mice fed a steady diet of protein containing 1% canavanine showed no change in lifespan.[3]

Alfalfa seeds and sprouts contain L-canavanine. The L-canavanine in alfalfa has been linked to lupus-like symptoms in primates, including humans, and other auto-immune diseases. Often stopping consumption reverses the problem.[4][5][6]

Tolerance

Some specialized herbivores tolerate L-canavanine either because they metabolize it efficiently (cf. L-canaline) or avoid its incorporation into their own nascent proteins.

By metabolic detoxification

Herbivores may be able to metabolize canavanine efficiently. The beetle Caryedes brasiliensis is able to break canavanine down to canaline, then further detoxifies canaline by reductive deamination to form homoserine and ammonia. As a result, the beetle not only tolerates the chemical, but uses it as a source of nitrogen to synthesize its other amino acids to allow it to develop.[7]

By selectivity

An example of this ability can be found in the larvae of the tobacco budworm Heliothis virescens, which can tolerate massive amounts of dietary canavanine. These larvae fastidiously avoid incorporation of L-canavanine into their nascent proteins (presumably by virtue of highly discriminatory arginine—tRNA ligase, the enzyme responsible for the first step in the incorporation of arginine into proteins). In contrast, larvae of the tobacco hornworm Manduca sexta can only tolerate tiny amounts (1.0 microgram per kilogram of fresh body weight) of dietary canavanine because their arginine-tRNA ligase has little, if any, discriminatory capacity. No one has examined experimentally the arginine-tRNA synthetase of these organisms. But comparative studies of the incorporation of radiolabeled L-arginine and L-canavanine have shown that in Manduca sexta, the ratio of incorporation is about 3 to 1.[8]

Dioclea megacarpa seeds contain high levels of canavanine. The beetle Caryedes brasiliensis is able to tolerate this however as it has the most highly discriminatory arginine-tRNA ligase known (as of 1982). In this insect, the level of radiolabeled L-canavanine incorporated into newly synthesized proteins is barely measurable. Moreover, this beetle uses canavanine as a nitrogen source (see above).[9]

See also

References

  1. ^ a b Akaogi, Jun; Barker, Tolga; Kuroda, Yoshiki; Nacionales, Dina C.; Yamasaki, Yoshioki; Stevens, Bruce R.; Reeves, Westley H.; Satoh, Minoru (2006). "Role of non-protein amino acid l-canavanine in autoimmunity". Autoimmunity Reviews. 5 (6): 429–35. doi:10.1016/j.autrev.2005.12.004. PMID 16890899.
  2. ^ Krakauer, J., et al. (2015). "Presence of l-canavanine in Hedysarum alpinum seeds and its potential role in the death of Christopher McCandless." Wilderness & Environmental Medicine. doi:10.1016/j.wem.2014.08.014
  3. ^ Brown, Dan L (2005). "Canavanine-induced longevity in mice may require diets with greater than 15.7% protein". Nutrition & Metabolism. 2 (1): 7. doi:10.1186/1743-7075-2-7. PMC 554090. PMID 15733319.
  4. ^ Montanaro, A; Bardana Jr, E. J. (1991). "Dietary amino acid-induced systemic lupus erythematosus". Rheumatic Disease Clinics of North America. 17 (2): 323–32. doi:10.1016/S0889-857X(21)00573-1. PMID 1862241.
  5. ^ Herbert, V; Kasdan, T. S. (1994). "Alfalfa, vitamin E, and autoimmune disorders". The American Journal of Clinical Nutrition. 60 (4): 639–40. doi:10.1093/ajcn/60.4.639. PMID 8092103.[unreliable medical source?]
  6. ^ http://vegpeace.org/rawfoodtoxins.html[full citation needed][permanent dead link][unreliable medical source?]
  7. ^ Rosenthal, Gerald A.; Dahlman, D. L.; Janzen, Daniel H. (3 November 1978). "L-Canaline Detoxification: A Seed Predator's Biochemical Mechanism". Science. 202 (4367): 528–529. doi:10.1126/science.202.4367.528.
  8. ^ Rosenthal, G. A.; Dahlman, D. L. (1986). "L-Canavanine and protein synthesis in the tobacco hornworm Manduca sexta". Proceedings of the National Academy of Sciences. 83 (1): 14–8. Bibcode:1986PNAS...83...14R. doi:10.1073/pnas.83.1.14. JSTOR 26787. PMC 322781. PMID 3455753.
  9. ^ Rosenthal, G. A.; Hughes, C. G.; Janzen, D. H. (1982). "L-Canavanine, a Dietary Nitrogen Source for the Seed Predator Caryedes brasiliensis (Bruchidae)". Science. 217 (4557): 353–5. Bibcode:1982Sci...217..353R. doi:10.1126/science.217.4557.353. PMID 17791516. S2CID 26741233.

Bibliography

  • Rosenthal, Gerald A. (1986). "Biochemical insight into insecticidal properties ofl-Canavanine, a higher plant protective allelochemical". Journal of Chemical Ecology. 12 (5): 1145–56. doi:10.1007/BF01639001. PMID 24307052. S2CID 37297952.
  • Rosenthal, G. A.; Berge, M. A.; Bleiler, J. A.; Rudd, T. P. (1987). "Aberrant, canavanyl protein formation and the ability to tolerate or utilize L-canavanine". Experientia. 43 (5): 558–61. doi:10.1007/BF02143585. PMID 3582574. S2CID 24239284.
  • Boyar, A.; Marsh, R. E. (1982). "L-Canavanine, a paradigm for the structures of substituted guanidines". Journal of the American Chemical Society. 104 (7): 1995–1998. doi:10.1021/ja00371a033.
  • Turner BL, Harborne JB (1967). "Distribution of canavanine in the plant kingdom". Phytochemistry. 6 (6): 863–866. Bibcode:1967PChem...6..863T. doi:10.1016/S0031-9422(00)86033-1. and in particularly large amounts in Canavalia gladiata (sword bean).
    • Ekanayake S, Skog K, Asp NG (May 2007). "Canavanine content in sword beans (Canavalia gladiata): analysis and effect of processing". Food and Chemical Toxicology. 45 (5): 797–803. doi:10.1016/j.fct.2006.10.030. PMID 17187914.

.........

This page was last edited on 4 December 2023, at 18:25
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.