Phenyl valerate

Candida cylindricae produces a lipase which will esterify L-menthol using 5-phenyl valeric add. 

Phenylheptanoate 9-Phenylnonanoate 11-Phenyldecanoate 9-Tolylnonanoate 5-(4-tolyl)valerate bi-phenyl) valerate pentanoate or 6-phenylhexanoate or 7-ph enylh eptano ate or 9-phenylnonanoate or 11-phenyldecano-ate... 

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]. 

Proof of the premise was found in the cyclization 7 of a-benzyl- 5-phenyl-valeric acid (XIII) and of a-benzyiglutaric add (XV) which gave the hydrindone derivatives XIV and XVI, respectively, and none of the isomeric benzosuberones. The formation of 4-phenylhydrindone-l from /3-2-biphenylpropionic acid afforded further substantiation, since the acid has the structural possibility of cyclizing to a seven-membered ring ketone. ... 

O Phenyl valerate is a colourless liquid that is used as a flavour and odorant. It contains 74.13% carbon, 7.92% hydrogen and 17.95% oxygen by mass. Determine the empirical formula of phenyl valerate. 

NTE was first identified as the presumptive target of neuropathic OP compounds in the initiation of OPIDN (Johnson, 1970). Its activity in cells and tissues is operationally defined as the enzymatic hydrolysis of the non-physiological substrate, phenyl valerate, which is resistant to inhibition by diethyl 4-nitrophenyl phosphate (paraoxon) and sensitive to inhibition by A.A -diisopropylphosphor-odiamidic fluoride (mipafox) under specified conditions of preincubation with inhibitors and subsequent incubation with substrate (Johnson, 1977 Kayyali et al., 1991 Makhaeva et al., 2007). 

FIGURE 57.11. Reaction of a serine esterase with phenyl valerate to yield phenol and valeric acid (Kayyali et al., 1991). 

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) ... 

In the study of mechanism of interaction of CarbE with some OPC in vitro it was found that this reaction is not irreversible, but reversible due to rapid spontaneous reactivation of inhibited CarbE [23, 53], The highest rate of spontaneous reactivation was obtained for plasma CarbE inhibited with sarin and the half time of reactivation was 18 minutes. These results were also confirmed in experiments in vivo in which rats were treated with 0.5 LD50 of soman, sarin and dichlorvos [53], Calculated half-times of reactivation for plasma CarbE of the rats treated with 0.5 LD50 dichlorvos, sarin and soman were 1.2, 2.0 and 2.7 hours, respectively. Spontaneous reactivation of CarbE hydrolyzing phenyl valerate inhibited with paraoxon in vitro was observed by Barril et al. [72],... 

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],... 

Measurement of NTE activity has classically been done by colorimetric determination of phenol released by hydrolysis of the substrate, phenyl valerate [89,90]. The absorbance maximum of the red phenol chromophore overlaps substantially with that of whole blood homogenates and dilution of the blood to remove the interfering absorbance decreases NTE activity below the detection limit of the colorimetric assay [88], Thus, the colorimetric assay cannot be used to assay NTE in whole blood. The problems inherent in a colorimetric NTE assay can be eliminated by using an amperometric technique to detect phenol. 

To create a fast and simple method for monitoring of human exposure to neuropathic OPs, a principal new approach to NTE activity analysis has been developed in joint study of the Institite of Physiologically Active Compounds Russian Acad. Sci. and Chemical Department of Moscow State University [88,91,92], Recently, a new biosensor for NTE assay was introduced using a tyrosinase carbon-paste electrode to detect phenol produced by the hydrolysis of phenyl valerate. In this type biosensor phenol is quantified by measuring electroreduction of the generated o-quinone on a graphite electrode (Fig. 6) [88,91 ]. The tyrosinase carbon-paste electrode improved the sensitivity of the NTE assay 10-fold compared to the colorimetric method or an earlier amperometric technique based on oxygen detection [92]. Moreover, the new electrode operates in a... 

Figure 5.6 A diagram showing neuropathy target esterase as a percentage of total esterase activity with phenyl valerate as the substrate.

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%. 

The simple diagram in Figure 5.6 shows this for the phenyl valerate-hydrolyzing enzymes in a homogenate of a hen s brain. 

The assay of NTE uses hen brain tissue, which contains substantial esterase activity with phenyl valerate substrate. It should include the use of comparative compounds that are neurotoxic (e.g., mipafox) and non-neurotoxic (e.g., paraoxon) as inhibitors of the enzyme for comparative purposes (Johnson 1977 Johnson and Riehardson 1983 Correll and Ehrich 1991 Richardson et al. 1993 Seifert and Wilson 1994). 

Seifert, J., and B. W. Wilson. 1994. Solubilization of neuropathy target esterase and other phenyl valerate carboxylesterases from chicken embryonic brain by phospholipase A2. Comparative Biochemistry and Physiology C 108 337-441. 

Milatovic. D., Moretto, A., Osman, K. A and Lotti, M, (1997), Phenyl valerate esterases other than neuropathy target c.sterase aod the promotion of organophosphate polyneuropathy, Cheit , Res. Toxicol. 10, 1045-1048. 

Moretlo, A,. Jokanovic, M., and Lotti, M, (1996). Inhibition of phenyl valerate esterases (PVE) sensitive to inipafox and promotion of organophosphate induced polyneuropathy (OPIDP). Toxicologi. 30, 300. 

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