Naphthyl acetate esterase

Induction of carboxylesterases and epoxide hydroloases would also affect the toxicity of insecticides. For example, host plant induction of 1-naphthyl acetate esterase would decrease the toxicity of certain insecticides containing an ester linkage such as organo-phosphates, pyrethroids, and some juvenile hormone analogs and, possibly, carbamates. 

The selective inhibition of JHE and omaphthyl acetate esterase(s) by ortho, meta and para substituted compounds showed that meta and para substitution offered selectivity towards JHE, however, the ortho substituted compounds favored inhibition of a-naphthyl acetate esterases (54). It was thought that substitution in the ortho position might be detrimental for inhibition of JHE. Therefore we decided to add Es value for the ortho substituents in the regression analysis to merge the ortho compounds with their meta and para analogs in the same regression, "Equation 37". 

It was possible for us to describe this clinical picture in detail from our own observations of a 13-year-old girl. We detected a very high content of cholesterol ester in the biopsy sample and a deficiency of lysosomal a-naphthyl-acetate esterase in the fibroblast culture. (205) (s. figs. 21.5 31.13, 31.14)... 

Based on the above discussion, trifluoromethyl ketones should inhibit proteases such as chymotrypsin (32), and serine esterases, such as acetylcholinesterase (33,24)> carboxylesterases (10), JHE and other esterases with varying selectivity. In a series of some juvenoid-like trifluoromethyl ketones and compounds of the structure A, l,l,l-trifluoro-2-tetradecanone (TFT) was found to be highly active and selective against JHE (I50 lxlO 7M) as compared to a-naphthyl acetate esterase (o-NaE) or trypsin (4iJ>). 

In 1982, the Schaap group demonstrated that chemiluminescence can be induced by the addition of a base to dioxetanes bearing a phenolic substituent [11]. Herein, the same group presents a method utilizing aryl esterase to catalyze the cleavage of a naphthyl acetate-substituted dioxetane in aqueous buffer at ambient... 

A few acetates of phenols have been used extensively as probes to investigate esterases, e.g., phenyl acetate (7.15), 4-nitrophenyl acetate (7.16), a-naphthyl acetate (7.17) and 7-acetoxy-4-mc(hyl-27/-[l bcnzopyran-2-onc (4-methylumbelliferyl acetate, 7.18). Such substrates are easy to handle and their phenolic metabolite is readily analyzed, allowing convenient monitoring of the reaction. 

The late discovery of acetyl xylan and feruloyl esterases has been partly due to the lack of suitable substrates. Xylans are often isolated by alkaline extraction, in which ester groups are saponified. Treatment of plant materials under mildly acidic conditions, as in steaming or aqueous-phase thermomechanical treatment, leaves most of the ester groups intact. These methods, however, partly hydrolyze xylan to shorter fragments (63,69). Polymeric acetylated xylan can be isolated from delignified materials by dimethyl sulfoxide extraction (70). The choice of substrate is especially important in studies of esterases for deacetylation of xylans. The use of small chromophoric substrates (p-nitrophenyl acetate, a-naphthyl acetate, and methylumbelliferyl acetate) analogously to the assays of disaccharidases may lead to the monitoring of esterases unable to deacetylate xylan (33, 63, 64). 

In this chapter we present the results from studying the possible inhibitory effects of PBO on the hydrolysis of 1-naphthyl acetate by putative pyrethroid resistance-related esterases in H. armigera and the resistance-related esterases in A. gossypii and M. persicae. 

At times l, 5, 10, 20, 30 and 40 minutes, 200 pL of buffer (as before) containing 1 mmol L" J-naphthyl acetate and 1,5 mmol I. 1 Fast Blue RR Salt were added to slop the inhibition and monitor the esterase activity remaining. This was performed by using a microplate reader (Molecular Devices) monitoring the assays at 450 nm for 10 minutes (Grant et al. 1989). 

The inhibitory effect of profenofos on esterase activity towards I-naphthyl acetate in the crude homogenates after a 30 min incubation, is shown in Fig. 13-1-There was some inhibition of esterase activity in the susceptible and ail the resistant strains (-20%) however, there was no inhibition with J-naphthyl acetate in the partially purified resistant enzyme extract. Increasing the profenofos beyond a threshold concentration of 0.64 pmol L 1 did not have any additional effect. 

Figure 13,1 Effecis of incubating resistant and susceptible H. ttrmigera homogenates, and a partially purified resistant enzyme extract with profcnofos. on esterase activity toward 1-naphthyl acetate.

Figure 13.3. Effects of incubation time on PBO inhibition of esterase-mediated hydrolysis of I-naphthyl acetate in resistant and susceptible H. armtgera homogenates and a partially perilied enzyme from the resistant strain.

Figure 13.4. Effects of incubation lime and PBO concentration on PBO inhibition of esterase-mediated hydrolysis oi [ -naphthyl acetate in homogenates of A. OJ. v/m ...

These esterases are classified as types A or B on the basis of their preferential hydrolysis of a- or 3- naphthyl acetate, respectively, in the presence of equal amounts of both substrates, after electrophoretic separation (22). ... 

Schaap, A. P., Handley, R. S., and Giri, B. P., Chemical and enzymatic triggering of 1,2-dioxetanes 1 Aryl esterase-catalyzed chemiluminescence from a naphthyl acetate-substituted dioxetane. Tetrahedron Lett. 28, 935-938 (1987). 

Aryl esterase (2-naphthyl acetate, 88, 87 500) lactonase (dihydrocoumarin, 6.5 x 10 )... 

M. expansa was cytosolic and conjugated CDNB but not bromobenzene or chlorobenzene (Douch and Buchanan 1978). Similarly, glutathione-S-transferase activity in H. contortus was observed only with CDNB as substrate and not with DCNB or l,2-epoxy-3-(p-nitrophenoxy)propane (Kawalek et al. 1984). Neither M. expansa not A. suum produced glucuronides with 4-nitrophenol, 2-aminophenol or 4-methylumbelliferone (Douch and Blair 1975), or possessed measurable DDT-dehydrochlorinase activity (Douch and Buchanan 1978). Various specific (cholinesterase) and non-specific esterases have been detected in trematodes, e.g. using a-naphthyl acetate as substrate, in A laria marcianae (Dickinson and Johnson 1978) and Schistosoma mansoni and Schistosoma haematobium (Coles 1970). 

Feruloyl Esterases. Psychrophilic feruloyl esterases are employed in industry for biomass degradation, biotransformation, and isolation of ferulic acid derivatives useful as antioxidant, antimicrobial, and photoprotectant properties. For instance, one studied feruloyl esterase from the psychrophilic bacterium, P. haloplanktis TAG 125, is a family 1 carbohydrate esterase and displays significant activity toward pNP-acetate, a- and yS-naphthyl acetate, and 4-methylumbelliferyl p-trimethylammonio cinnamate chloride (a model substrate for determining ferulolyl esterase activity) (23). 

Almost 200 pesticides were analyzed in various systems using dichloromethane and ethyl acetate (129). These pesticides were visualized by the following selective detection methods (a) o-tolidine-potassium iodide, (b) p-nitro-benzene-diazonium-fluoborate, (c) silver nitrate with UV irradiation, (d) p-dimethylaminobenzaldehyde, (e) bioassays with either fungispores of Aspergillus nigeror an enzyme inhibition method. When horse blood serum was the enzyme source, acetylcholine iodide was its substrate in the presence of 2,6-dichloro-phenol-indophenol. Naphthyl acetate was applied as the substrate for the human blood plasma esterases. The Rf values and detection limits were also published (129). 

Cacco and Maggioni have described the extraction and partial purification of arylesterases active against a-naphthyl acetate. Fractionation by electrophoresis in polyacrylamide gels yielded several esterase-active bands, each of which contained coloured humic compounds. The... 

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