Oscillatoria formosa

H omoanatoxin-a] Oscillatoria formosa (blue-green nACh-R blocker (respiratory... 

Homoanatoxin-a, obtained from various freshwater cyanobacteria, is a relatively rare natural analog of anatoxin-a for which the C-11 side chain is extended by one methylene unit (Figure 6.4). It was originally isolated from Planktothrix sp. (formerly Oscillatoria) in 1992 [51]. It has recently been isolated from Raphidiopsis mediterranea Skuja from Japan [52] and Planktothrix (formerly Oscillatoria) formosa blooms in Ireland [53]. 

Biosynthesis of homoanatoxin-a was examined using Oscillatoria formosa and a mechanism similar to that for anatoxin-a was proposed [13,14]. The origin of the C-12 methyl group that distinguishes homoanatoxin-a from anatoxin-a, was shown through feeding experiments performed with L-[methyl- C]-methionine in the culture of Raphidiopsis mediterranea Skuja. It was proposed that the S-methyl of methionine is transferred to the toxin via S-adenosyl-L-methionine (SAM)-mediated methylation [55]. 

In 1992, a methylene analogue of AN, named homoanatoxin-a (HMAN), was isolated from Planktothrix (Oscillatoria) formosa in Norway (Skulberg et al. 1992). Interestingly, HMAN... 

Lilleheil, G., Andersen, R.A., Skulberg, O.M., and Alexander, I 1997. Effects of a homoanatoxin-a-containing extract from Oscillatoria formosa (Cyanophyceae/cyanobacteria) on neuromuscular transmission. Toxicon 35, 1275-1289. 

In 1992, a methylene analogue of AN, homoanatoxin-a (HMAN) (Figure 38.1 R=C2H5), was isolated from Planktothrix (Oscillatoria) formosa in Norway (Skulberg et al., 1992). AN and HMAN act by enhancing the release of acetylcholine (ACh) from peripheral cholinergic nerves (Lilleheil et al, 1997). HMAN is much less common than AN but has been found in Ireland and Japan (Furey et al., 2003a), (Namikoshi et al., 2003). Anatoxin-a(s) is structurally umelated to AN but was also... 

Hemscheidt T, Rapala J, Sivonen K, Skulberg OM (1995) Biosynthesis of anatoxin-a in Anabaena flos-aquae and homoanatoxin-a in Oscillatoria formosa. J Chem Soc Chem Commun 13 1361-1362. doi 10.1039/C39950001361... 

Valentine et al., 1991). Anatoxin-a is stable under sterile conditions but is susceptible to microbial biodegradation (Rapala et al., 1994). Breakdown is also accelerated by high temperature, UV light, and alkaline conditions (Kaminski et al., 2013 Stevens and Krieger, 1991). The half-life in a reservoir was reported to be 5 days under typical environmental pH conditions (Smith and Sutton, 1993). A structural analog, called homoanatoxin-a or methylene-anatoxin-a, has been isolated from Oscillatoria formosa (Skulberg et al., 1992). Small quantities of anatoxin-a are produced synthetically for use in acetylcholine (ACh) receptor research (Aronstam and Witkop, 1981). 

Oryzaephilus surinamensis, 4094 Oryzalin, 198 Oryza saliva, 1569, 3587 Oscillatoria, 47 O.formosa, 42 O. nigro-viridis, 1293 Oscillatoriales, 59 Oscine, 349... 

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