Electric eel acetylcholinesterase

Fig. 28.3. Reproduced from Fig. 3 of Ref. [45], with permission from Elsevier. Detection of organo-phosphates extracted from wool, (a) Extracts containing either chlorfenvinphos (C) or diazinon (D) numbers are X in 10-XM. (b) Extracts containing mixtures of the two total concentration of organo-phosphates was 10-5M. Electrodes were exposed to the extracts, dried overnight and the currents generated in the presence of butyrylthiocholine measured. White columns, electric eel acetylcholinesterase grey, bovine erythrocyte acetylcholinesterase and black, horse serum butyryl cholinesterase.

Acharya, J., Gupta, A.K., Mazumder, A., Dubey, D.K. (2008a). In vitro reactivation of sarin inhibited electric eel acetylcholinesterase by bis-pyridinium oximes bearing methoxy ether linkages. Toxicol. In Vitro 22 525-30. 

Next, Danishefsky s allosamizoline synthesis will be described [143,144]. The key point of their synthetic strategy is the utilization of enzymatic optical resolution to the racemic substrate. As illustrated in O Fig. 8, there are two approaches for the enzymatic optical resolution. One is the enzymatic hydrolysis of a diester [145,146,147], and the other is the enzymatic transacylation of the meso-dk> [148,149,150] (O Fig. 8). In Danishefsky s group, the former route was chosen as the key step. Treatment of diacetate 186 with electric eel acetylcholinesterase provided the monoacetate 187, which was reported by Deardorrf et al. [147]. This work was also applied to the synthesis of PG p2a in Danishefsky s laboratory [151]. On the basis of the success of their synthesis of PG p2a, diacetate 188, which was derived from the 2-alkene-l,4-diol derivative 176, was treated with electric eel acetylcholinesterase as well. Interestingly, this treatment provided the unexpected monoacetate 189 in 95% yield, > 95% ee (O Fig. 8). 

Anticholinesterase activity was measured against electric eel acetylcholinesterase by the method previously described (19). 

Most of the published studies of AN-a(s) in cyanobacteria have involved live animal bioassays a study using mice showed that this toxin has an LD50 of approximately 50 fig/kg (i.p.) (Mahmood and Carmichael, 1986). The same authors also observed the acetyl chohnesterase inhibition that is characteristic of AN-a(s). The inhibitory effect of this toxin remains the most effective means of detection and has been exploited in an assay using electric eel acetylcholinesterase (Mahmood et al., 1988) and in a number of subsequent bioassays. Although the inhibitory effect of AN-a(s) is similar to synthetic organophosphate insecticides, it was shown that AN-a(s) as an active site-directed... 

A biosensor based on the electrochemical detection of the activity of electric eel acetylcholinesterase was developed. Disposable amperometric sensors were produced that gave a detection limit of 1 pg AN-a(s)/L. Oxime reactivation was also used to discriminate between the toxin and potential insecticides present in water samples (Villatte et al., 2002). 

S.2.2 Routes Employing Late-Stage C-3/N Bond Formation In prior methodological studies, Mariano and coworkers had reported an interesting photochemical conversion of pyridinium perchlorate (438) into meso-4-acetylamino-3,5-acetoxycyclopentene (439), and its desym-metrization by enantioselective enzymatic hydrolysis with electric eel acetylcholinesterase to give (+)-440 in 80% They subsequently reported... 

A final example shows a process called desymmetrization (Figure 15.25). We start with a raeso-compound (remember this is a molecule that contains asymmetric carbon atoms but is not chiral, because it has a plane of symmetry) with two identical functional groups. Under enzymatic hydrolysis, only one of these reacts, so a chiral compound is produced, and all the material is used, without any need to recycle. The enzyme used in this reaction is electric eel acetylcholinesterase (EEAc). Pig liver esterase is also commonly used, as a relatively crude extract is inexpensive and gives good results. An example is shown in Figure 15.26, in the synthesis of 7 -mevalonolactone, important in the biosynthesis of terpenes and steroids. 

Studies conducted thus far to develop synthetic apphcations of this chemistry have relied heavily on the earlier finding that the tra s,tra s-amidocyclopentenyl acetate 40 can be prepared readily by irradiation of pyridine in aqueous acid solution (Scheme 14). This substance is functionally similar to compounds that have been converted to non-racemic mono-alcohols by enzymatic desymmetrization processes. Thus, treatment of diacetate 40 with the electric eel acetylcholinesterase (EEACE) was found to generate the mono-ester 41 in a 68% yield and 80% ee (Scheme 16). In addition, Mariano and coworkers have demonstrated that stereochemical diversity can be introduced into the aminocyclopentene ring system using hydroxyl inversion procedures.An example of this is found in the conversion of 41 to its ds-trans-diastereomer 42 by employment of the amide directed inversion method developed by Wipf and co-workers " (Scheme 16). These observations have estabhshed the foundation for applications of pyridinium salt photochemistry to the synthesis of the biomedically important aminocyclopentitols and aminoaldopentoses shown in Schemes 17,18 and 19.13.15-17... 

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