Antimycin A

Antimycin A
Names
IUPAC name
(2R,3S,6S,7R,8R)-3-[(3-Formamido-2-hydroxybenzoyl)amino]-8-hexyl-2,6-dimethyl-4,9-dioxo-1,5-dioxonan-7-yl 3-methylbutanoate
Other names
Fintrol
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.162.279
MeSH Antimycin+A
Properties
C28H40N2O9
Molar mass 548.63 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Antimycins are a group of secondary metabolites produced by Streptomyces bacteria.[1] It is classified as an extremely hazardous substance in the United States, as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[2]

Use

Antimycin A is the active ingredient in Fintrol, a chemical piscicide (fish poison) used in fisheries management.[3]

Antimycin A was first discovered in 1945 and registered for use as a fish toxicant in 1960.[4] Fintrol ® is the only currently registered product containing Antimycin A and is classified as a restricted use pesticide because of its aquatic toxicity and requirement for highly specialized training in order to use it. In 1993, several toxicology studies were submitted to the United State Environmental Protection Agency yielding its toxicity.[4]

Fintrol is used primarily by federal and state governments in order to eliminate invasive species in an area where resident species are threatened. Antimycin A is added drop-wise in order to reach a concentration of 25 parts per billion.[4] These drip stations are typically used upstream in an area that is accessible to boats and traffic. In deeper bodies of water, a pump mechanism is used to disperse Antimycin A through a perforated hose stretching the length of the water column.

In aquaculture, Antimycin A is used as an agent to enhance catfish production via selective killing small and more sensitive species. When Antimycin A is added at 25 ppb it provides a complete kill. However at 10 ppb, Antimycin A is used as a selective killing agent to kill smaller or more sensitive species that may reduce the yield of commercial farming.

Products Containing Antimycin A can be registered providing they follow risk mitigation procedures.[4]

Risk of ConcernMitigation Measures
Exposure from consuming treated water
  • Flowing water must be treated with potassium permanganate
  • Drinking water within the treatment areas must be closed during treatment and until all monitoring of samples is below the limit of Antimycin A detection, 0.015 parts per billion
Exposure from consuming treated fish
  • The certified applicator or designee under his/her direct supervision must prohibit consumption of dead fish taken from treatment areas.
  • The registrant must amend labels to specify maximum treatment concentrations of 10 ppb for use as a ‘selective kill’ in aquaculture.
  • When Antimycin A is applied as a selective kill in aquaculture, the Certified Applicator must inform the owner/operator of the aquaculture site being treated that surviving fish must not be harvested for food or feed for a minimum of 12 months after treatment.
  • When Antimycin A is applied as a complete kill in aquaculture, the Certified Applicator must inform the owner/operator of the aquaculture site being treated that the water body must not be restocked for a minimum of 7 days after treatment
Exposure from recreational activities in the treated water
  • The certified applicator or his/her designee must prohibit access to treated area for 7 days following treatment.
Occupational Exposure
  • The registrant must specify maximum treatment levels of 25 ppb
  • Anitmycin A must be applied by a certified applicator who attends a certification program for piscicide applications.
  • The applicator is required to wear long sleeved shirt and long pants, chemical resistant gloves, closed toed shoes and socks, and protective eyeware. Applicators using handheld equipment like a nozzle must wear a dust/mist respirator and coveralls. The applicator should not be wearing contact lenses.
Ecological Risk Quotients for non-target species
  • Antimycin A is forbidden to be used in marine or estuarine environments
  • The certified applicator or designee must ensure treatment does not pass beyond the designated treatment area
  • The certified applicator or designee should collect and bury any dead fish

To date there has been no usage in human medicine, although its possibility as a chemotherapeutic was explored.[4]

Mechanism of action

Antimycin A is an inhibitor of cellular respiration, specifically oxidative phosphorylation. Antimycin A binds to the Qi site of cytochrome c reductase, inhibiting the oxidation of ubiquinone in the Qi site of ubiquinol thereby disrupting the Q-cycle of enzyme turn over. Cytochrome c reductase is a central enzyme in the electron transport chain of oxidative phosphorylation.[5] The inhibition of this reaction disrupts the formation of the proton gradient across the inner membrane of the mitochondria. The production of ATP is subsequently inhibited, as protons are unable to flow through the ATP synthase complex in the absence of a proton gradient. This inhibition also results in the formation of the toxic free radical superoxide.[6] The rate of superoxide production exceeds the cellular mechanisms to scavenge it, overwhelming the cell and leading to cell death.

It has also been found to inhibit the cyclic electron flow within photosynthetic systems along the proposed ferredoxin quinone reductase pathway.[7]

Although cyanide acts to block the electron transport chain, Antimycin A and cyanide act in different mechanisms. Cyanide binds a site in neighboring protein where iron normally binds, preventing oxygen from binding at all. This prevents cellular respiration completely leading to cell death.[8] Because Antimycin A binds to a specific protein in the electron transport chain, its toxicity can be highly species dependent because of subtle species specific differences in ubiquinol. This is why Fintrol can be used a selective killing agent in commercial farming.

Fungus-growing attine ants have been shown to use antimycins - produced by symbiotic Streptomyces bacteria - in their fungiculture, to inhibit non-cultivar (i.e. pathogenic) fungi.[9] One research group studying these symbiotic Streptomyces bacteria recently identified the biosynthetic gene cluster for antimycins, which was unknown despite the compounds themselves being identified 60 years ago. Antimycins are synthesised by a hybrid polyketide synthase (PKS)/non-ribosomal peptide synthase (NRPS).[10]

Toxicity

Lethal Doses

Lethal Doses in Fish Species [11]

SpeciesLC50/24 hours exposureLC50/96 hours exposure
Trout0.07ppb0.04ppb
Black Bullhead Catfish200ppb45ppb
Channel Catfish>10ppb9ppb
Goldfish1ppb
Snails800ppb
Tiger salamander>1080ppb
Tadpoles45ppb10ppb
Leopard Frog45ppb10ppb

Lethal Doses in Mammals [12]

AnimalLD50 mg/kg ingested
Rat28
Mouse25
Lamb1-5
Dog>5
Rabbit10

Human Exposure and First Aid

Exposure to Treated Water: The effects of chronic, sub-lethal human exposure have estimated and extrapolated from murine(=pertaining to rodents ) toxicology studies. Estimates in the literature have been determined using EPA risk assessment protocols.[13] Studies aimed at determining these levels found a concentration in mice where there is "No Observed Adverse Effect Level." From there, the EPA describes methods to determine a reference dose (RfD), the upper limit of the substance that can be consumed daily for the rest of one's life without any observable consequences. The RfD was determined to be 1.7micrograms/kg/day.[14] For a grown adult, weighing around 70 kg, they can safely consume 2 liters of treated water at 60ppb.

Toxic effects may result from accidental ingestion of the material. Animal toxicology studies suggest that exposure to less than 40 grams of Antimycin A can result in serious adverse health effects to the individual.[15]

Route of ExposureEffect
Eye
  • Direct contact to the eye may result in discomfort with tearing and redness. There may be slight abrasion and the Antimycin has the potential to produce a foreign body sensation in some individuals.
Skin
  • Open cuts should not be exposed to the material.
  • It is crucial that good hygiene practices are followed to prevent abrasion from prolonged exposure
Inhaled

Treatment is focused on relieving symptoms and monitoring for respiratory distress, pulmonary edema, seizures, and shock.[15] Emesis after ingestion is not recommended for the potential of central nervous system depression.[16] Activated charcoal can be given as 240mL of water with 30g of charcoal.[16] The patient should be monitored for development of systemic symptoms and signs. After inhalation the patient should be moved to fresh air and monitored for bronchospasm, difficulty breathing, and respiratory distress. If needed, provide the patient with oxygen and secure an airway via tracheal intubation. Treat bronchospasm with inhaled beta2-adrenergic agonist and severe bronchospasm can be treated with systemic corticosteroids.[16]

Biosynthesis

Part 1
Part 2

Antimycins are produced as secondary metabolites by Streptomyces bacteria, a soil bacteria. These specialized metabolites likely function to kill neighboring organisms in order to provide the streptomyces bacteria with a competitive edge.[17] Antimycins are produced by a non-ribosomal peptide synthetase (NRPS)/polyketide synthase (PKS) assembly complex which acts as an assembly line for antimycin production. The assembly is genetically coded for by the ant gene family. The assembly requires 14 proteins, AntBCDEFGHIJKLMNO, which shuttle the intermediates along the assembly line through a series of transesterifications, keto reductions, thiolations (addition of a sulfur containing group), condensations, and adenylations.[18] The last two steps involving AntB and AntO are tailoring steps. The following steps describe chemically what the Ant Enzymes do in order to synthesize Antimycin. Synthesis begins with tryptophan, an amino acid.

1. The indole ring of tryptophan, an amino acid, is opened by a pathway-specific tyrptophan-2.3-dioxygnease, AntN, to make N-formyl-L-kynurenine.[19]

2. N-formyl-L-kynurenine is converted to anthranilate by the pathway-specific kynureninase, AntP.[19]

3. Anthranilate is activated by the acyl-CoA ligase protein, AntF and loaded onto its cognate carrier protein, AntG, for further processing.[19]

4. Anthranilate is converted to 3-aminosalicylate by a multicomponent oxygenase, AntHIJKL.[19]

5. 3-Aminosalicylate is presented to the NRPS, AntC. AntC has two modules which are organized Condensation1 (C1) -Adenylation1 (A1) -Thiolation1 (T1) -Condensation2 (C2) -Adenylation2 (A2) -Ketoreduction (KR) -Thiolation2 (T2). The A1 domain activates and loads threonine, an amino acid, onto T1, followed by a C1 promoted condensation of 3-aminosalicylate and threonine. The A2 domain activates and loads pyruvate onto T2. Pyruvate is reduced by the KR domain and condensed with threonine by C2 [17]

6. The Ketosynthase domain of PKS catalyses the decarboxylative condensation between the aminoacyl thioester attached to AntC T2 domain and the 2-carboxy-acyl moiety attached to AntD Acetyl Carrier Protein domain.[17]

7. AntM catalyses the reduction of the β-keto group, which precedes the AntD TE domain – promoted release of the nine-membered dilactone [17]

8. A lipase homologue, AntO, and acyltransferase homologue, AntB, catalyze the installation of the N-formyl group and the transesterification of the C-8 hydroxyl group, respectively, resulting in the backbone for the Antimycin family.[17]

References

  1. ↑ Neft N, Farley TM (March 1972). "Conditions influencing antimycin production by a Streptomyces species grown in chemically defined medium". Antimicrob. Agents Chemother. 1 (3): 274–6. doi:10.1128/aac.1.3.274. PMC 444205. PMID 4558141.
  2. ↑ "40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities" (PDF) (July 1, 2008 ed.). Government Printing Office. Retrieved October 29, 2011.
  3. ↑ "Fintrol concentrate". PAN Pesticides Database - Pesticide Products. Retrieved 9 February 2010.
  4. 1 2 3 4 5 Caulkins, Peter. "Reregistration Eligibility Decision for Antimycin A" (PDF). United States EPA. Retrieved April 17, 2017.
  5. ↑ Kim, Hoeon; Esser, Lothar; Hossain, M. Bilayet; Xia, Di; Yu, Chang-An; Rizo, Josep; van der Helm, Dick; Deisenhofer, Johann (1999). "Structure of Antimycin A1, a Specific Electron Transfer Inhibitor of Ubiquinol−CytochromecOxidoreductase". Journal of the American Chemical Society. 121 (20): 4902–4903. doi:10.1021/ja990190h. ISSN 0002-7863.
  6. ↑ Dairaku N, Kato K, Honda K, et al. (March 2004). "Oligomycin and antimycin A prevent nitric oxide–induced apoptosis by blocking cytochrome C leakage". J. Lab. Clin. Med. 143 (3): 143–51. doi:10.1016/j.lab.2003.11.003. PMID 15007303.
  7. ↑ Taira, Yoshichika (1 January 2013). "Antimycin A-like molecules inhibit cyclic electron transport around photosystem I in ruptured chloroplasts". FEBS Open Bio. 3 (1): 406–410. doi:10.1016/j.fob.2013.09.007.
  8. ↑ Ott, Kevin. "Antimycin. A Brief Review of It's Chemistry, Environmental Fate, and Toxicology" (PDF).
  9. ↑ Schoenian, I.; et al. (2011). "Chemical basis of the synergism and antagonism in microbial communities in the nests of leaf-cutting ants". Proc Natl Acad Sci USA. 108 (5): 1955–1960. doi:10.1073/pnas.1008441108. PMC 3033269. PMID 21245311.
  10. ↑ Yu, Jae-Hyuk; Seipke, Ryan F.; Barke, Jörg; Brearley, Charles; Hill, Lionel; Yu, Douglas W.; Goss, Rebecca J. M.; Hutchings, Matthew I. (2011). "A Single Streptomyces Symbiont Makes Multiple Antifungals to Support the Fungus Farming Ant Acromyrmex octospinosus". PLoS ONE. 6 (8): e22028. doi:10.1371/journal.pone.0022028. ISSN 1932-6203.
  11. ↑ Ott, Kevin. "Antimycin. A Brief Review of It's Chemistry, Environmental Fate, and Toxicology" (PDF).
  12. ↑ Ott, Kevin. "Antimycin. A Brief Review of It's Chemistry, Environmental Fate, and Toxicology" (PDF).
  13. ↑ Draft EIS, Flathead Westslope Cutthroat Trout Project. June 2004. p. Chapter 3.
  14. ↑ J. O. Kuhn, “Final Report. Acute Oral Toxicity Study in Rats”, Stillmeadow, Inc., Submitted to Aquabiotics Corp. (March 2001)
  15. 1 2 "Material Safety Data Sheet - Antimycin A" (PDF). Santa Cruz Biotechnology.
  16. 1 2 3 "Antimycin A". TOXNET. National Institutes of Health.
  17. 1 2 3 4 5 Seipke, Ryan F; Hutchings, Matthew I (2013). "The regulation and biosynthesis of antimycins". Beilstein Journal of Organic Chemistry. 9: 2556–2563. doi:10.3762/bjoc.9.290. ISSN 1860-5397.
  18. ↑ Yan, Yan; Zhang, Lihan; Ito, Takuya; Qu, Xudong; Asakawa, Yoshinori; Awakawa, Takayoshi; Abe, Ikuro; Liu, Wen (2012). "Biosynthetic Pathway for High Structural Diversity of a Common Dilactone Core in Antimycin Production". Organic Letters. 14 (16): 4142–4145. doi:10.1021/ol301785x. ISSN 1523-7060.
  19. 1 2 3 4 Sandy, Moriah; Rui, Zhe; Gallagher, Joe; Zhang, Wenjun (2012). "Enzymatic Synthesis of Dilactone Scaffold of Antimycins". ACS Chemical Biology. 7 (12): 1956–1961. doi:10.1021/cb300416w. ISSN 1554-8929.
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