118:) of the CB subunit is important for the interaction between both subunits as it interacts with an alpha helix of CA. The CA subunit thereby blocks a part of the enzyme surface of phospholipase A2, resulting in an impossibility to be activated. This means the phospholipase A2 cannot adsorb onto a lipid/water interface from the cell membrane. Residues on the CB subunit which are involved in the enzyme surface and blocked by the CA subunit are F24 and F119, which are
215:) of native crotoxin is 0.096 μg/g in mice. It has been reported that mice can develop a tolerance to the toxin when they get increasing doses of crotoxin every day. They can eventually tolerate doses up to 35 times the LD50 without being intoxicated. Preclinical studies on human patients also show that toxicity signs decreased or disappeared when the patients were exposed to crotoxin over longer periods of time.
69:). The first publication of this discovery showed that the toxin worked with two elements, a toxic and a coagulating principle. Later it was discovered that the crotoxin protein is not homogeneous, but consists of two subunits. The toxic effect of crotoxin is determined mainly by the phospholipase A2 action of CB. The CA subunit is non-enzymatic and non-toxic, but has blood coagulating functions (
180:
receptors either agonistic or antagonistic, inducing pharmacological effects non-enzymatically. The intracellular PLA2 could also remain enzymatically active and hydrolyze membrane phospholipids. This could lead to pharmacological effect by means of the damage to the membranes and membrane proteins, or by the lysophospholipids and
257:), some studies have already been conducted to investigate whether Crotoxin could function as a therapy for muscle tension problems. In one study, Crotoxin has shown to improve the ocular alignment of a group of cross-eyed patients after injection. The same study has also shown that it might help patients with
141:
The different isoforms of both subunits CA and CB can form crotoxin complexes which can be subdivided into two classes: moderately toxic with a high phospholipase A2 activity or more toxic with a lower enzymatic activity. The isoforms thereby also play a role in the stability of the crotoxin complex.
197:
are blocked by the heterodimeric form of crotoxin. This blocking is achieved by a stabilization of the inactive form of the nicotinic acetylcholine receptors by the enzyme complex. Together with the presynaptic acetylcholine inhibition, this post synaptic effect can lead to paralysis of the affected
184:
released in hydrolysis. The final hypothesis is based on the induced changes in Ca2+-concentrations in affected cells. The large changes in the Ca2+-concentrations interfere with many processes, including vesicle fusion and the mitochondrial membrane potential. Both these processes are important for
231:
is a specifically developed antivenom that has to be injected intravenously. With the arrival of this antivenom, the fatality rate declined from 73% to 1.5%. The dosage of the antivenom varies between 10 and 20 ampules depending on the severity of the envenoming. However, the efficacy of the doses
244:
venom is a potent neurotoxin, which also causes renal- and myotoxic effects. Except for its toxic effects, crotoxin also shows anti-inflammatory, immunomodulatory, anti-HIV and anti-tumor effects in human and animal models. Together with the fact that the body can build up tolerance to the toxic
206:
Crotoxin has fatal neurotoxic effects, as the toxicity of CB is synergistically intensified by CA. Many people die of acute renal failure or acute respiratory failure. The latter is a result of muscle paralysis in the respiratory system. Low crotoxin levels produce an incomplete blockage of the
179:
and the depletion of the acetylcholine store. Another hypothesis is based on the specific binding with receptors and proteins to create intracellular enzyme dependent and independent reactions. Membrane damage by the PLA2 activity allows PLA2 to enter cells and specifically bind to proteins and
162:
The presynaptic acetylcholine secretion inhibition is caused by the phospholipase A2 activity of the CB subunit. The exact mechanism of presynaptic acetylcholine inhibition by
Phospholipase A2 (PLA2) is not known. While the presynaptic effect is caused by the CB subunit, it is enhanced by the
551:
142:
Less toxic complexes are less stable while the more toxic complexes are more stable. The more toxic crotoxin complexes therefore dissociate more slowly than the less toxic ones. The relation between toxicity and enzyme activity is a result of the synergistic manner (
81:
The structure of crotoxin is composed by the components CA and CB in a 1:1 molecular ratio.܁CA is a nontoxic and non-enzymatic acidic protein while CB is the toxic component, a phospholipase A2 protein. Both components form a noncovalent heterodimeric complex
106:) with loops at the terminal positions are formed by the α and β chains. The γ chain forms a disordered loop. Component CA is present in the heterodimeric complex to prevent the binding of the phospholipase A2 to nonspecific binding sites.
174:
There is a hypothesis based on the damage that PLA2 does to membrane phospholipids via hydrolysis at the specific binding sites on exocytotically active parts of the membrane. This could lead to interference with the reabsorption of
552:"Neuromuscular Paralysis by the Basic Phospholipase A 2 Subunit of Crotoxin from Crotalus Durissus Terrificus Snake Venom Needs Its Acid Chaperone to Concurrently Inhibit Acetylcholine Release and Produce Muscle Blockage"
794:
329:
146:) of action of both subunits. For this the CA subunit enhances the toxicity of the CB subunit while it reduces its enzyme activity and anticoagulant activity.
850:
815:
892:
693:"Time factor in the detection of circulating whole venom and crotoxin and efficacy of antivenom therapy in patients envenomed by Crotalus durissus"
719:
Cura JE, Blanzaco DP, Brisson C, Cura MA, Cabrol R, Larrateguy L, Mendez C, Sechi JC, Silveira JS, Theiller E, Roodt AR de, Vidal JC (2002).
643:
490:"Structure and Function Relationship of Crotoxin, a Heterodimeric Neurotoxin Phospholipase A2 from the Venom of a South-American Rattlesnake"
207:
acetylcholine receptor resulting in paresis, which is fully reversible. At higher doses, neuromuscular impairment is more severe. Also other
421:"Relationship between the structure and the enzymatic activity of crotoxin complex and its phospholipase A2 subunit: An in silico approach"
211:
symptoms are common, especially at higher doses. Intramuscular injection of crotoxin further shows myotoxic effects. The intravenous LD50 (
556:
273:
production. Some studies have shown crotoxin to improve symptoms related to immune-associated disease and other conditions, including
444:"Crystal Structure of Crotoxin Reveals Key Residues Involved in the Stability and Toxicity of This Potent Heterodimeric β-Neurotoxin"
466:
194:
868:
621:"Calcium Influx and Mitochondrial Alterations at Synapses Exposed to Snake Neurotoxins or Their Phospholipid Hydrolysis Products"
533:
471:
425:
73:), now known as crotapotin. Since 1966 until today, investigations into pharmacological applications for crotoxin are conducted.
492:, In: Singh B.R., Tu A.T. (eds), Natural Toxins 2, Advances in Experimental Medicine and Biology, vol 391. Springer, Boston, MA.
625:
176:
269:. Clinical research has shown that the crotoxin complex and isolated CB have antigenic characteristics, which can stimulate
62:. These researchers found that 60 per cent of the venom consisted of a neurotoxic substance, later referred to as crotoxin.
171:
There are some hypotheses and models that try to explain the pharmacological effects of phospholipase A2 (PLA2) activity.
832:
467:"Comparison of crotoxin isoforms reveals that stability of the complex plays a major role in its pharmacological action"
379:
Sampaio SC, Hyslop S, Fontes MRM, Prado-Franceschi J, Zambelli VO, Magro AJ, Brigatte P, Gutierrez VP, Cury Y (2010).
325:"Biochemistry and Pharmacology of the Crotoxin Complex: I. Subfractionation and Recombination of the Crotoxin Complex"
254:
355:"Biophysical studies suggest a new structural arrangement of crotoxin and provide insights into its toxic mechanism"
748:
528:
692:
667:"Crotoxin, the Neurotoxin of South American Rattlesnake Venom, is a Presynaptic Toxin Acting Like β-Bungarotoxin"
420:
278:
725:
503:"Pancreatic and Snake Venom Presynaptically Active Phospholipases A2 Inhibit Nicotinic Acetylcholine Receptors"
721:"Phase I and Pharmacokinetics Study of Crotoxin (cytotoxin PLA2, NSC-624244) in Patients with Advanced Cancer"
720:
790:"Effects of crotoxin, a neurotoxin from Crotalus durissus terrificus snake venom, on human endothelial cells"
744:"Effect of membrane composition and of co-encapsulation of immunostimulants in a liposome-entrapped crotoxin"
502:
66:
691:
Amaral CFS, Campolina D, Dias MB, Bueno CM, Chávez-Olortegui C, Penaforte CL, Diniz CR, Rezende NA (1997).
887:
575:"Different Mechanisms of Inhibition of Nerve Terminals by Botulinum and Snake Presynaptic Neurotoxins"
380:
743:
771:
489:
359:
212:
55:
154:
The primary mechanistic action of crotoxin is twofold, a presynaptic and a postsynaptic action.
193:
The second part of the mechanism of action of crotoxin is the postsynaptic part. Postsynaptic
38:, composed of an acidic, non-toxic and non-enzymatic subunit (CA), and a basic, weakly toxic,
25:
846:"Immunotherapeutic potential of Crotoxin: anti-inflammatory and immunosuppressive properties"
598:"Excitement Ahead: Structure, Function and Mechanism of Snake Venom Phospholipase A2 Enzymes"
671:
306:
39:
266:
87:
42:
protein (CB). This neurotoxin causes paralysis by both pre- and postsynaptic blocking of
666:
324:
845:
881:
766:
648:
448:
258:
119:
83:
54:
Crotoxin was identified in 1938 by researchers of the
Department of Chemistry of the
43:
31:
133:
amino acids which play an important role in the stability of the crotoxin complex.
767:"Crotoxin promotes macrophage reprogramming towards an antiangiogenic phenotype"
208:
181:
123:
103:
70:
20:
831:
International
Application Published Under the Patent Cooperation Treaty (PCT).
816:"Crotoxin in humans: analysis of the effects on extraocular and facial muscles"
130:
115:
35:
742:
Magalhaes T, Proietti Viotti A, Teperino Gomes R, Viana de
Freitas T (2001).
597:
789:
574:
443:
354:
262:
99:
620:
403:
301:
245:
effects of crotoxin, these effects are of interest for pharmaceutical use.
265:
show normal function. Therefore, it is proposed as a good alternative for
122:
amino acids. It however was found that these residues are not part of the
507:
270:
697:
602:
579:
385:
143:
274:
281:) supported clinical trials studying crotoxin for cancer treatment.
788:
de
Andrade CM, Rey FM, Cintra ACO, Sampaio SV, Torqueti MR (2019).
465:
Faure G, Harvey AL, Thomson E, Saliou B, Radvanyi F, Bon C (1993).
851:
Journal of
Venomous Animals and Toxins including Tropical Diseases
488:
Choumet V, Bouchier C, Délot E, Faure G, Saliou B, Bon C (1996).
58:
in São Paulo. The compound was first purified from the venom of
529:"Postsynaptic Effects of Crotoxin and of Its Isolated Subunits"
114:
The CB subunit is a phospholipase A2 protein. The C-terminal (
814:
Barros
Ribeiro G de, Almeida HC de, Toledo Velarde D (2012).
90:) of CA and CB can form at least 16 distinct CTX complexes.
65:
Crotoxin was the first proteinic toxin to be crystallized (
261:. At low concentrations of crotoxin, patients with muscle
765:
de Araújo
Pimenta L, de Almeida MES, Bretones ML et al.
223:
In Brazil, each year almost 2,000 snakebites are due to
381:"Crotoxin: Novel activities for a classic β-neurotoxin"
102:-bonded polypeptide chains: α, β and γ. Alpha-helices (
833:"International Publication Number: WO 2009/018643 A2"
541:(3), 471–482. doi:10.1111/j.1432-1033.1979.tb13278.x.
479:(2), 491-496. doi:10.1111/j.1432-1033.1993.tb17946.x.
227:. The only treatment for people who are envenomed by
129:The interface between CA and CB is formed by three
795:International Journal of Biological Macromolecules
656:(3-4), 165-170. doi:10.1080/15569543.2016.1220397.
393:(6), 1045-1060. doi:10.1016/j.toxicon.2010.01.011.
802:(1), 613-621. doi:10.1016/j.ijbiomac.2019.05.019.
404:"Pharmacology of crystalline crotoxin - toxicity"
610:(8), 827–840. doi:10.1016/j.toxicon.2003.11.002.
587:(5), 561–564. doi:10.1016/j.toxicon.2008.12.012.
349:
347:
345:
343:
779:, 4281 (2019). doi:10.1038/s41598-019-40903-0.
633:(15), 11238–11245. doi:10.1074/jbc.m610176200.
323:Rübsamen K, Breithaupt H, Habermann E (1971).
253:As Crotoxin works as a neuromuscular blocker (
810:
808:
687:
685:
375:
373:
330:Naunyn-Schmiedebergs Archiv für Pharmakologie
8:
456:(2), 176-191. doi:10.1016/j.jmb.2011.07.027.
302:"Two Active Proteins from Rattlesnake Venom"
296:
294:
715:
713:
711:
426:Journal of Molecular Graphics and Modelling
844:Sartim MA, Menaldo DL, Sampaio SV (2018).
523:
521:
822:(6). doi:10.1590/S0004-27492012000600002.
419:Pereanez JA, Gómez ID, Patino AC (2012).
818:, Arquivos Brasileiros de Oftalmologia,
433:, 36-42. doi:10.1016/j.jmgm.2012.01.004.
564:, 8–17. doi:10.1016/j.taap.2017.08.021.
550:Cavalcante, Walter L.g., et al (2017).
515:(10), doi:10.1371/journal.pone.0186206.
290:
277:. However, there are currently no NCI (
367:, 43885 (2017). doi:10.1038/srep43885.
353:Fernandes C, Pazin W, Dreyer T et al.
501:Vulfius, Catherine A., et al (2017).
7:
858:(39). doi:10.1186/s40409-018-0178-3.
665:Chiung Chang C, Dong Lee J (1977).
557:Toxicology and Applied Pharmacology
314:, 213 (1938). doi:10.1038/142213a0.
232:have not been clinically examined.
23:of the South American rattlesnake,
573:Montecucco, Cesare, et al (2009).
406:, Memórias do Instituto Butantan,
98:The CA protein is formed by three
19:is the main toxic compound in the
14:
644:"Toxin synergism in snake venoms"
195:nicotinic acetylcholine receptors
893:Acetylcholine release inhibitors
869:"Clinical Trials Using Crotoxin"
534:European Journal of Biochemistry
472:European Journal of Biochemistry
626:Journal of Biological Chemistry
619:Rigoni, Michela, et al (2007).
442:Faure G, Xu H, Saul FA (2011).
300:Slotta, KH, Fraenkel-Conrat H.
86:). It was found that isoforms (
1:
871:, retrieved on 16 March 2020.
527:Bon, Cassian, et al (1979).
163:presence of the CA subunit.
867:National Cancer Institute.
835:, Published: 6 August 2008.
596:Kini, R Manjunatha (2003).
402:Vital Brazil et al (1966).
255:Neuromuscular-blocking drug
249:Pharmaceutical applications
185:acetylcholine homeostasis.
909:
749:Biotechnol. Appl. Biochem.
279:National Cancer Institute
726:Clinical Cancer Research
77:Structure and reactivity
67:Protein crystallization
60:Crotalus d. terrificus
642:Laustsen AH (2016).
150:Mechanism of action
772:Scientific Reports
360:Scientific Reports
213:Median lethal dose
56:Instituto Butantan
225:Crotalus durissus
26:Crotalus durissus
900:
872:
865:
859:
842:
836:
829:
823:
812:
803:
786:
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763:
757:
740:
734:
717:
706:
689:
680:
672:Arch. Pharmacol.
663:
657:
640:
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617:
611:
594:
588:
571:
565:
548:
542:
525:
516:
499:
493:
486:
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457:
440:
434:
417:
411:
400:
394:
377:
368:
351:
338:
321:
315:
298:
40:phospholipase A2
30:. Crotoxin is a
908:
907:
903:
902:
901:
899:
898:
897:
878:
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876:
875:
866:
862:
843:
839:
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826:
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741:
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519:
500:
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487:
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464:
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441:
437:
418:
414:
401:
397:
378:
371:
352:
341:
322:
318:
299:
292:
287:
267:botulinum toxin
251:
238:
221:
204:
191:
169:
160:
152:
139:
112:
96:
88:Protein isoform
79:
52:
12:
11:
5:
906:
904:
896:
895:
890:
880:
879:
874:
873:
860:
837:
824:
804:
781:
758:
735:
707:
681:
658:
635:
612:
589:
566:
543:
517:
494:
481:
458:
435:
412:
395:
369:
339:
316:
289:
288:
286:
283:
250:
247:
237:
234:
220:
217:
203:
200:
190:
187:
168:
165:
159:
156:
151:
148:
138:
135:
111:
110:The CB subunit
108:
95:
94:The CA subunit
92:
78:
75:
51:
48:
17:Crotoxin (CTX)
13:
10:
9:
6:
4:
3:
2:
905:
894:
891:
889:
886:
885:
883:
870:
864:
861:
857:
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852:
847:
841:
838:
834:
828:
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811:
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797:
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791:
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782:
778:
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773:
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759:
755:
751:
750:
745:
739:
736:
732:
728:
727:
722:
716:
714:
712:
708:
705:(5), 699-704.
704:
700:
699:
694:
688:
686:
682:
678:
674:
673:
668:
662:
659:
655:
651:
650:
649:Toxin Reviews
645:
639:
636:
632:
628:
627:
622:
616:
613:
609:
605:
604:
599:
593:
590:
586:
582:
581:
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563:
559:
558:
553:
547:
544:
540:
536:
535:
530:
524:
522:
518:
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510:
509:
504:
498:
495:
491:
485:
482:
478:
474:
473:
468:
462:
459:
455:
451:
450:
449:J. Mol. Biol.
445:
439:
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317:
313:
309:
308:
303:
297:
295:
291:
284:
282:
280:
276:
272:
268:
264:
260:
259:blepharospasm
256:
248:
246:
243:
235:
233:
230:
226:
218:
216:
214:
210:
201:
199:
196:
188:
186:
183:
178:
172:
166:
164:
157:
155:
149:
147:
145:
136:
134:
132:
127:
125:
121:
120:phenylalanine
117:
109:
107:
105:
101:
93:
91:
89:
85:
84:Protein dimer
76:
74:
72:
68:
63:
61:
57:
49:
47:
45:
44:acetylcholine
41:
37:
33:
32:heterodimeric
29:
27:
22:
18:
888:Snake toxins
863:
855:
849:
840:
827:
819:
799:
793:
784:
776:
770:
761:
753:
747:
738:
733:, 1033-1041.
730:
724:
702:
696:
676:
670:
661:
653:
647:
638:
630:
624:
615:
607:
601:
592:
584:
578:
569:
561:
555:
546:
538:
532:
512:
506:
497:
484:
476:
470:
461:
453:
447:
438:
430:
424:
415:
407:
398:
390:
384:
364:
358:
334:
328:
319:
311:
305:
252:
241:
240:Crotoxin in
239:
228:
224:
222:
205:
192:
189:Postsynaptic
173:
170:
161:
153:
140:
128:
113:
97:
80:
64:
59:
53:
46:signalling.
24:
16:
15:
242:C. durissus
229:C. durissus
209:cholinergic
182:fatty acids
158:Presynaptic
124:active site
104:Alpha helix
71:Coagulation
21:snake venom
882:Categories
679:, 159-168.
410:, 973-980.
337:, 274-288.
285:References
167:Hypotheses
137:Reactivity
131:tryptophan
116:C-terminus
36:neurotoxin
28:terrificus
263:dystonias
219:Treatment
198:muscles.
100:disulfide
756:, 61-64.
508:PLOS One
271:antibody
236:Efficacy
202:Toxicity
177:vesicles
698:Toxicon
603:Toxicon
580:Toxicon
386:Toxicon
144:Synergy
50:History
307:Nature
275:cancer
34:beta-
800:134
677:296
631:282
562:334
477:214
454:412
335:270
312:142
884::
856:24
854:,
848:,
820:75
807:^
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792:,
775:,
769:,
754:33
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723:,
710:^
703:35
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684:^
675:,
669:,
654:35
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629:,
623:,
608:42
606:,
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577:,
560:,
554:,
539:99
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531:,
520:^
513:12
511:,
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452:,
446:,
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429:,
423:,
408:33
391:55
389:,
383:,
372:^
363:,
357:,
342:^
333:,
327:,
310:,
304:,
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126:.
777:9
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