Insect toxin

Insect toxins Inside battery limit m situ Diagnostics... 

A possible example of this thesis is the crystalline insect toxin found in Bacillus thuringiensis spores and discussed here by Dr. Anderson. Although neither the bacillus nor its spores exhibit useful antibiotic activity against other microorganisms, the very specific toxicity to insects has become of major commercial interest. The enormous number and variety of fungal species available for further examination must lead inevitably to one or more which produces pesticidal metabolites. 

Animal Sources. The marine annelid worm Lumbrineris hetero-poda produces an insect toxin nereistoxin, 24, 4-N,N-dimethyl-amino-1,2-dithiolane (5 ). The mink MusteXa vison) affords 2,2-dimethylthietane, 14, and 3,3-dimethy1-1,2-dithiolane, 25 (28,63, 64), the ferret Musteta putoris) secretes 14, 25, cis- and trans-2,3-dimethylthietane, 2-propyl- and 2-pentyl-thietane, cis and trans-3,4-dimethyl-l,2-dithiolane, and 3-propyl-l,2-dithiolane (65), and the stoat (Mustela erminea) contains 2-ethyl-, 2-propyl-, and 2-pentyl-thietane, and 3-ethyl- and 3-propyl-l,2-dithiolane in its anal gland (5, ). These several thiaheterocycles from mustela species probably function as scent markers. 

There are many different kinds of toxicants. Chemicals that are used for industrial and household purposes can be poison when misused or when there is an accident. Agricultural pesticides in the field can also cause poisoning. Chemicals might come in the form of conventional drugs which we use in a legitimate way, or in the form of designer drugs used illicitly for recreational substance abuse. Natural toxins found in the environment, such as mushrooms, plant toxins, snake/insect toxins and marine toxins, can also inadvertently harm a patient. 

What are the advantages and disadvantages of introducing genes coding for insect-toxins into major crop plants ... 

I.S. Blagbrough and E. Moya, Animal Venoms and Insect Toxins as Lead Compounds for Agrochemicals , in Crop Protection Agents from Nature natural products and analogues , ed. L.G. Copping, Royal Society of Chemistry, Cambridge, UK, 1996, pp. 339-359. 

Structures of hallactones A and B, insect toxins from Podocarpus hallii. Russell, G. B. Fenemore, P. G. Singh, P. J. Chem. Soc. Chem. Commun. 1973,166-167. 

Bacillus Sp. These bacteria are gram-positive soil microbes. Members of the Bacillus species supply 58% of industrial enzymes sold (19). For example, proteases from B. amjloliquefaciens and amylases from B. licheniformis, glucose isomerase from B. coagulans are used in a variety of industrial processes (see Enzyme APPLICATIONS-INDUSTRIAL). The proteinaceous inclusions produced by B. thuringiensis are useful as insect toxins. Thus extensive fermentation technology has been developed for Bacillus species and low cost media are available (19). 

Toxins and other natural products generally provide great benefit to society. For example, some of the most widely used drugs and therapeutics like streptomycin, the aminoglycoside antibiotic from soil bacteria, and acetylsalicylic acid (aspirin), the nonsteroidal anti-inflammatory from willow tree bark, are used by millions of people everyday to improve health and well-being. On the other hand, adverse encounters with toxins like fish and shellfish toxins, plant, and insect toxins do result in harm to humans. 

One of the most well-known examples of insect toxins is melittin, a bee venom peptide with potent haemolytic activity. Melittin adopts an a-helical conformation, and has been extensively characterised using a range of techniques, including both solution- and solid-state NMR spectroscopy.176 Some helical peptides with antimicrobial activity have also been found in wasps, such as eumenine mastroparan-AF (EMP-AF-NH2) from the venom of the solitary wasp Anterhynchium flavormarginatum micado,177 and the cecropins found in the haemolymph of Hyalophora cecropia.178 Several of these peptides have cytotoxic activity and are potential anticancer agents.179... 

BmKocITOl, oc-insect toxin from venom of the Chinese scorpion B. martensii Karsch Conkunitzin-s2, cone snail neurotoxin... 

The total synthesis of pederin, a potent insect toxin was achieved by T. Takemura and co-workers. One of the key steps of the synthesis was an intramolecular samarium diiodide induced Reformatsky reaction to construct the lactone subunit of the molecule. The transformation was carried out in tetrahydrofuran at 0 °C without the use of additives or catalysts. 

Takemura, T., Nishii, Y., Takahashi, S., Kobayashi, J. i., Nakata, T. Total synthesis of pederin, a potent insect toxin the efficient synthesis of the right half, (+)-benzoylpedamide. Tetrahedron 2002, 58, 6359-6365. 

Gupta S, Krasonoff SB, Underwood NL, Renwick JAA, Roberts DW. Isolation of beauvericin as an insect toxin from Fusarium semitectum and Fusarium moniliforme var. subglutinums. Mycopathologia 115 185-189, 1991. 

The advent of contemporary biotechnology has enabled development of new strategies to achieve the same objectives protecting crops using biolr cally-produced, biodegradable pestiddes. A typical example is die production and use of proteinaceous insect toxins encoded by Baculo virus. Th fyp pestiddes are readitylnpgradable and are target spedfic. 

Recombinant Baculoviruses Expressing Insect Toxins. The first attempt to modify a NPV for increased insecticidal activity was conducted by Carbonell et al 33) in which an insect-specific toxin (BelT) from the scorpion Buthus eupus was incorporated into the AcNPV genome. Although low levels of toxin expression were confirmed, the recombinant NPV did not result in quicker killing rates of host insects. Failure to improve killing activity may be due to an insufficient level of toxin expression by AcNPV, an incorrect sequence of toxin DNA, and/or insufficient or incorrect folding of the toxin following expression. 

The Insect-Selective Neurotoxin, AalT. The North African scorpion, Androctonus australis Hector, possesses three classes of toxins in its venom. One of these classes is specific for insects although one anti-insect toxin has been shown to induce a response in both insect and mammalian systems (41). A. australis possess an insect toxin (AalT) which is a single chained polypeptide composed of seventy amino acids (Mr = 8kDa) cross linked by four disulfide bridges (42). The insect selectivity of AalT has been documented by toxicity, binding and electrophysiological assays (43), and studies with mice have shown that 50 mg/kg (subcutaneous) produced no adverse physiological symptoms (44). 

Donovan, W.P., C. Dankocsik, M.P. Gilbert, M.C. Gawron-Burke, R.G. Groat, and B.C. Carlton. 1988. Amino acid sequence and entomocidal activity of the P2 crystal protein, an insect toxin from Bacillus thuringiensis var. kurstaki. J. Biol. Chem. 263 561-567. 

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