Ester phenyl valerate

The esterase got the names neurotoxic esterase or neuropathy target esterase, and the ester phenyl valerate (PV) was found to be a good substrate for this esterase. However, PV is also hydrolyzed by other esterases because paraoxon, which does not give symptoms of delayed neurotoxicity, inhibited the PV activity as much as 80%. The NTE is defined as the hydrolytic activity against PV that is not inhibited by paraoxon but by mipafox. About 3% of the activity is not inhibited by mipafox plus paraoxon. Thus, the part of PV activity due to neurotoxic esterase should be 17%. 

Other studies on the PFR in the presence of cyclodextrins include substrates with different acyl moieties (phenyl propionate and phenyl valerate) [261] 1-naphthyl acetate [262,263], 1-naphthyl benzoate [263], sulfonate esters, [264,265], benzenesulfonylanilides [266], acetanilide [259,267], and benzanilide [259,268]. 

NTE is operationally defined as the esteratlc activity against phenyl phenylvalerate (the preferred substrate), phenyl valerate, or closely related esters that is "resistant" to paraoxon and sensitive to DFP and nlpafox (N,N -dlisopropylphosphorodlaniidlc fluoride) ... 

NTE is an integral membrane protein in neurons and some non-neural cell types of vertebrates [3,27,32] and its activity depends on lipid contents. It is present in all neurons, but is absent from glia [32], NTE can hydrolyze many esters of carboxylic acids. NTE is conveniently detected in vitro by its ability to catalyse OP-sensitive hydrolysis of an artificial substrate, phenyl valerate. Its activity is operationally defined as phenyl valerate hydrolysis resistant to inhibition by 0,0-diethyl-4-nitrophenyl phosphate (paraoxon, non-neuropathic) and sensitive to inhibition by NJ T-diisopropyl phosphorodiamidic fluoride (mipafox, neuropathic), determined under specified conditions [3]. Differential centrifugation of brain homogenates resulted in an enrichment of NTE in microsomal fractions containing elements of endoplasmic reticulum (ER), Goldgi, and plasma membrane [39],... 

The natural reaction substrates and products of serine esterases are not electrochemically active. To transduce these esterase activities into an electrical signal, a two-enzyme reaction pathway can be assembled on a gold electrode. In the first reaction, the esterase of interest converts a phenyl ester (e.g., phenyl valerate) into phenol (Figure 63.11). In the second reaction, tyrosinase converts phenol first to catechol, and then to o-quinone (Figure 63.12), which can be electrochemically reduced back to catechol at an electrode, yielding a measurable current (Eq. (63.17)) (Kohli et al., 2007a, 2010). 

The mesogenic units with methylenic spacers were prepared by reacting the sodium salt of either 4-methoxy-4 -hydroxybiphenyl or 4-phenylphenol with a bromoester in DMF at 82° C for at least 4 hours in the presence of tetrabutylammonium hydrogen sulfate (TBAH) as phase transfer catalyst. In this way, ethyl 4-(4-oxybi-phenyl)butyrate, ethyl 4-(4-methoxy-4 -oxybiphenyl)butyrate, ethyl 4-(4-oxybiphenyl)valerate, ethyl 4-(4-methoxy-4 -oxybiphenyl)-valerate, n-propyl 4-(4-oxybiphenyl)undecanoate and n-propyl 4-(4-methoxy-4 -oxybiphenyl)undecanoate were obtained. These esters were hydrolyzed with base and acidified to obtain the carboxylic acids. The corresponding potassium carboxylates were obtained by reaction with approximately stoichiometric amounts of potassium hydroxide. Experimental details of these syntheses were described elsewhere (27). 

An interesting intramolecular nucleophilic displacement is the first-order neighboring participation of the NMe2 group during the hydrolysis of 4-substituted phenyl esters of y-(iV,iV -dimethylamino)butyric and valeric acids (reaction 15) The rate constant for the formation... 

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