Blarina toxin

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Blarina toxin ( Blarina brevicauda )
Mass / length primary structure 253 amino acids
Precursor (282 aa)
Identifier
External IDs
Enzyme classification
EC, category 3.4.21. ,  Serine proteinase
MEROPS S01.409
Response type Cleavage of peptide bonds
Substrate Kininogen
Products Kallidin

Blarina toxin , abbreviated to BLTX , is an animal poison . It is found in representatives of the American short-tailed shrews , after whose generic name Blarina it is named, in the saliva and in the lower jaw salivary glands . In addition, scorpion-crusty lizards have a structurally, biochemically and functionally almost identical poison in the lower lip glands, which is known as gilatoxin . This means that BLTX is not only one of the few poisons that occur in mammals , but from a phylogenetic point of view also emerged independently of one another in two different animal groups. The poison, which functions as a serine protease and is similar to the body's own enzyme kallikrein , is used by short-tailed shrews to paralyze and kill prey . In humans, a bite from these animals generally does not cause serious symptoms.

properties

Blarina toxin was first described in 1942 and detected in the saliva and the mandibular salivary gland of the northern short-tailed shrew Blarina brevicauda . The molar mass of the active form consisting of 253 amino acids , which is formed from a preform of 282 amino acids, is 28 kilodaltons . From a functional point of view, it is a serine protease that converts kininogens into kinins and is probably evolutionarily derived from the KLK1 variant of the body's own enzyme kallikrein . It can be inhibited by aprotinin , among other things ; the proteolytic activity is essential for the poisonous effect. The pH optimum is 9.0.

The structurally, biochemically and functionally almost identical and also called gilatoxin -like component of the poison of the scorpion-crustacean lizard ( Heloderma horridum ), which has a molecular mass of around 33 kilodaltons compared to the form from Blarina brevicauda , consists of 245 amino acids.

effect

Blarina brevicauda

The lethal dose (LD 50 ) of Blarina toxin, which mainly affects the central nervous system , is around one milligram per kilogram of body weight when injected intraperitoneally in mice and about 0.1 to 0.2 milligrams per kilogram of body weight when injected intravenously in rabbits . Depending on the amount of poison, the effects include general malaise, burning pain, swelling and redness at the bite site, breathing disorders , a drop in blood pressure due to widening of the blood vessels, as well as cramps and paralysis . Death occurs through paralysis of the respiratory center . The toxicity of the poison in one bite is sufficient to kill smaller vertebrates such as other shrews , mice and voles , salamanders and frogs, and songbirds , which are among the prey of the American short-tailed shrews . In most cases, it paralyzes prey, which also includes snails and earthworms . These survive up to five days in a coma-like state, which means that short-tailed shrews can build up supplies of unspoiled animal food. The effect of a short-tailed shrew bite in humans is limited to local symptoms at the bite site and for this reason has no clinical relevance worth mentioning.

Gilatoxin in the venom of the scorpion-crustacean , which is almost identical to Blarina toxin, has almost the same lethality in purified form as the complete venom of the lizard, in which it only accounts for around three to five percent. In addition to gilatoxin, the poison of the scorpion lizard contains other components such as phospholipase A₂ , an analogue of the vasoactive intestinal peptide (VIP) and hyaluronidase activity , which increases the absorption and distribution of the poison in the tissue. When a scorpion lizard bites, in comparison to the blarina toxin of the short-tailed shrews, due to the more complex composition as well as the larger amount of poison and the direct release of the poison into the bite wound via corresponding teeth, further and more serious symptoms can occur. These include general weakness, nausea and vomiting as well as increased sweating and fever for several hours and, in rare cases, a sharp drop in blood pressure and shock . Deaths after Heloderma bites are described in older publications, but they are likely to be attributed to unfavorable circumstances such as poor general condition of those affected.

Individual evidence

  1. ↑ a b Yael T. Aminetzach, John R. Srouji, Chung Yin Kong and Hopi E. Hoekstra: Convergent Evolution of Novel Protein Function in Shrew and Lizard Venom. ( Memento of the original from September 24, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 895 kB) In: Current Biology. Published online October 29, 2009. Elsevier, doi : 10.1016 / j.cub.2009.09.022 . @1@ 2Template: Webachiv / IABot / www.oeb.harvard.edu
  2. ^ A b Sydney Ellis, Otto Krayer: Properties of a Toxin From the Salivary Gland of The Shrew, Blarina brevicauda. In: Journal of Pharmacology and Experimental Therapeutics . 114 (2) / 1955, pp. 127-137, ISSN  0022-3565 .
  3. ↑ a b c d e f Masaki Kita, Yasuo Nakamura, Yuushi Okumura, Satoshi D. Ohdachi, Yuichi Oba, Michiyasu Yoshikuni, Hiroshi Kido, Daisuke Uemura: Blarina Toxin, a Mammalian Lethal Venom From The Short-tailed Shrew Blarina brevicauda: Isolation and characterization. In: Proceedings of the National Academy of Sciences . 101 (20) / 2004, pp. 7542-7547, ISSN  0027-8424 .
  4. ↑ Åke Lundwall, Maria Brattsand: Kallikrein-Related Peptidases. In: Cellular and Molecular Life Sciences. 65 (13) / 2008, pp. 2019-2038, ISSN  1420-682X .
  5. ↑ Robert A. Hendon, Anthony T. Tu: Biochemical Characterization of The Lizard Toxin Gilatoxin. In: Biochemistry . 20 (12) / 1981, pp. 3517-3522, ISSN  0006-2960 .
  6. ↑ Pongsak Utaisincharoen, Stephen P. Mackessy, Roger A. Miller, and Anthony T. Tu: Complete Primary Structure and Biochemical Properties of Gilatoxin, a Serine Protease with Kallikrein-like and Angiotensin-degrading Activities. In: Journal of Biological Chemistry . 268 (29) / 1993, pp. 21975-21983, ISSN  0021-9258 .
  7. ^ Joseph F. Merritt: Advances in the biology of shrews II. Special publication of the International Society of Shrew Biologists, Lulu.com, 2005, ISBN 9781411678187 , pp. 361-366.
  8. ↑ Northern Short-Tailed Shrew (Blarina brevicauda). In: Charles Fergus: Wildlife of Pennsylvania and the Northeast. Stackpole Books, Mechanicsburg 2000, ISBN 0-81-172899-4 , pp. 16/17.
  9. ↑ a b Northern Short-Tailed Shrew (Blarina brevicauda). In: Allen Kurta, William Henry Burt: Mammals of the Great Lakes Region. University of Michigan Press, Ann Arbor 1995, ISBN 0-47-206497-5 , pp. 46-49
  10. ↑ a b Stephen B. Vander Wall: Animal Storage. In: Food Hoarding in Animals. University of Chicago Press, Chicago 1990, ISBN 0-22-684735-7 , pp. 86-88.
  11. ↑ Michael R. Dobbs: Clinical Neurotoxicology: Syndromes, Substances, Environments. Saunders / Elsevier, Philadelphia 2009, ISBN 0-32-305260-6 , pp. 475/476.
  12. ↑ a b c d Clinical Toxicology of Helodermatidae Lizard Bites. In: Jürg Meier, Julian White: Handbook of Clinical Toxicology of Animal Venoms and Poisons. CRC Press, Boca Raton 1995, ISBN 0-84-934489-1 , pp. 360-366.

literature

  • Masaki Kita, Yasuo Nakamura, Yuushi Okumura, Satoshi D. Ohdachi, Yuichi Oba, Michiyasu Yoshikuni, Hiroshi Kido, Daisuke Uemura: Blarina Toxin, a Mammalian Lethal Venom From The Short-tailed Shrew Blarina brevicauda: Isolation and Characterization. In: Proceedings of the National Academy of Sciences . 101 (20) / 2004. National Academy of Sciences, pp. 7542-7547, ISSN  0027-8424
  • Dietland Müller-Schwarze: Chemical Ecology of Vertebrates. Cambridge University Press, Cambridge 2006, ISBN 0-52-136377-2 ; Chapter 10: Allomones I: Chemical Defense by Animals. Section 10.5: Mammals. Pp. 262-264