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PubMed1998

Action of Trichoderma reesei and Aspergillus oryzae esterases in the deacetylation of hemicelluloses.

Xylans and mannans contain different esterified substituents such as acetyl, feruloyl and p-coumaroyl side groups. The functions of hemicellulose-deacetylating esterases of Trichoderma reesei and Aspergillus oryzae are discussed in this paper. Both fungi produce multiple esterases and two different esterases were isolated from both T. reesei and A. oryzae. The enzymes differed significantly in their substrate specificities. Acetyl xylan esterase of T. reesei was highly active on polymeric xylan but was unable to remove acetyl substituents from glucomannan or phenolic substituents from wheat straw arabinoxylan. Another esterase, acetyl esterase from T. reesei, had activity only towards short oligomeric and monomeric acetates derived both from xylan and glucomannan. The acetyl glucomannan esterase of A. oryzae was most active towards polymeric glucomannan, but was also able to remove acetyl groups from xylan. The only esterase studied which was active against phenolic substituents in arabinoxylans was the feruloyl esterase from A. oryzae. Feruloyl esterase had the widest substrate specificity of the esterases studied. It was also able to act on acetyl groups both in xylan and in glucomannan. The simultaneous enzymic liberation of acetyl groups from xylan and glucomannan clearly enhanced the action of xylan- and mannan-degrading enzymes, thus increasing the hydrolysis yield significantly. However, none of the esterases was able to remove all acetyl substituents when acting alone and simultaneous action of two esterases was needed for complete deacetylation.

Acetates↗
PubMed1981

Nonspecific esterase in human lymphocytes.

A substantial proportion of human peripheral lymphocytes exhibits esterase activity as demonstrated by cytochemical techniques using hexazotized pararosanilin as coupling agent and different alpha-naphthyl compounds, in particular alpha-naphthyl-acetate, as substrates. Esterase-positive lymphocytes showed one or several dots of the reaction product. Plasma cells and macrophages also exhibited marked esterase activity but with diffuse distribution of the reaction product throughout the cytoplasm. The substrate specificity, the time course and the pH optimum of the cytochemical reaction were determined. The results indicate that these lymphocyte esterases are identical with acid lipases. The number of esterase-positive cells reaches a plateau well below 100% (85% for blood lymphocytes) even with optimal staining procedures. The relation between esterase activity and other so-called lymphocyte markers such as sIg and the capacity to form spontaneous rosettes with sheep red blood cells was investigated in peripheral human blood lymphocytes. A fair correlation between rosette formation and esterase activity was found and most of the esterase-positive cells were sIg-negative. However, the fit was never complete. The results suggest that esterase activity is largely characteristic for small peripheral T cells. Almost all blast cells formed following stimulation with Con A or PHA were esterase-positive. Histochemical studies showed that the large majority of the thymocytes in the cortex lacked esterase activity. In lymph nodes, a low proportion of esterase-positive cells was found in the germinal centers, whereas most lymphocytes in the paracortical are were esterase-positive.

Adolescent↗
PubMed1993

Association of two esterase genes, a chromosomal inversion, and susceptibility to Plasmodium cynomolgi in the African malaria vector Anopheles gambiae.

The ability of a selected strain of the malaria vector Anopheles gambiae to encapsulate the early oocysts of the malaria parasite Plasmodium cynomolgi B has previously been shown to be genetically linked to specific esterase phenotypes. This association between Plasmodium susceptibility and esterase phenotype is found in the An. gambiae G3 strain from which the Plasmodium-refractory and -susceptible mosquito strains were derived. Genetic crosses had suggested that the esterase phenotypes reflect the assortment of two alleles at one esterase genetic locus, with the two esterase homozygotes showing Plasmodium-susceptible and -refractory phenotypes and the esterase heterozygote being intermediate in susceptibility. By using a variety of specific esterase inhibitors in conjunction with esterase staining of gel-electrophoresed mosquito homogenates, we found that the bands previously thought to reflect one genetic locus are actually the product of two different esterase loci, Est1, a cholinesterase, and Est2, a carboxylesterase. In addition, examination of chromosomal inversions and the esterase phenotype in the An. gambiae G3 strain revealed that different forms of a polymorphic inversion on the left arm of chromosome two (the 2La inversion) are inseparably associated with different alleles at these two esterase loci. We conclude that the genetic association among the esterase-linked Plasmodium-susceptibility locus and the two esterase loci is maintained by the suppression of recombination in 2La inversion heterozygotes in the An. gambiae G3 strain and its selected derivatives.

Alleles↗
PubMed2005

Regulation of JH epoxide hydrolase versus JH esterase activity in the cabbage looper, Trichoplusia ni, by juvenile hormone and xenobiotics.

JH III esterase and JH III epoxide hydrolase (EH) in vitro activity was compared in whole body Trichoplusia ni homogenates at each stage of development (egg, larva, pupa and adult). While activity of both enzymes was detected at all ages tested, JH esterase was significantly higher than EH activity except for day three of the fifth (last) stadium (L5D3). For both enzymes, activity was highest in eggs. Adult virgin females had 4.6- and 4.0-fold higher JH esterase and EH activities, respectively, than adult virgin males. JH III metabolic activity also was measured in whole body homogenates of fifth stadium T. ni that were fed a nutritive diet (control) or starved on a non-nutritive diet of alphacel, agar and water. With larvae that were starved for 6, 28 and 52 h, EH activity per insect equivalent was 48%, 5% and 1%, respectively, of the control insects. At the same time points, JH esterase activity levels in starved T. ni were 29%, 4% and 3% of that of insects fed the nutritive diet. Selected insect hormones and xenobiotics were administered topically or orally to fifth stadium larvae for up to 52 h, and the effects on whole body EH and JH esterase activity analyzed. JH III increased the JH III esterase activity as high as 2.2-fold, but not the JH III EH activity. The JH analog, methoprene, increased both JH esterase and EH activity as high as 2.5-fold. The JH esterase inhibitor, 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP), had no impact on EH activity. The epoxides trans- and cis-stilbene oxide (TSO and CSO) in separate experiments increased the EH activity approximately 2.0-fold. TSO did not alter JH esterase levels when topically applied, but oral administration reduced activity to 70% of the control at 28 h, and then increased the activity 1.8-fold at 52 h after the beginning of treatment. CSO had no effect on JH esterase activity. Phenobarbital increased EH activity by 1.9-fold, but did not change JH esterase levels. Clofibrate and cholesterol 5alpha,6alpha-epoxide had no effect on EH. JH esterase activity also was not affected by clofibrate, but cholesterol 5alpha,6alpha-epoxide reduced the JH esterase activity to 60-80% of the control. The biological significance of these results is discussed.

Animals↗
PubMed2001

Preliminary characterisation of esterase and platelet-activating factor (PAF)-acetylhydrolase activities from cat flea (Ctenocephalides felis) salivary glands.

Naphthyl esterase and platelet-activating factor (PAF)-acetylhydrolase activities were detected in the salivary glands of the cat flea, Ctenocephalides felis. Salivary naphthyl esterase activity is disgorged during exploratory probing. Whole extracts of salivary glands contain esterase activity against the short-chain naphthyl esters alpha-naphthyl acetate (approximately 210pmol/min/gland pair; 10.0micromol/min/mg specific activity; K(m) approximately 59microM) and beta-naphthyl acetate (approximately 110pmol/min/gland pair; 5.2micromol/min/mg specific activity; K(m) approximately 132microM). Salivary gland extracts have PAF-acetylhydrolase activity (approximately 5pmol/min/gland pair; 0.24micromol/min/mg specific activity) but do not have detectable acetylcholinesterase activity. Native-PAGE and IEF resolve three and six salivary gland naphthyl esterase bands, respectively, and both patterns are different from carcass esterases. Salivary gland naphthyl esterase activity binds reversibly to Concanavalin A, and enzymatic deglycosylation with glycopeptidase F produced a new, fast-migrating salivary gland naphthyl esterase band on Native-PAGE. Renaturation of esterase activity after SDS-PAGE gave approximately 56kDa, approximately 57kDa and approximately 58kDa naphthyl-esterase-positive bands. On gel filtration naphthyl esterase and PAF-acetylhydrolase activities co-elute as a single peak with an apparent molecular weight of approximately 59kDa. This partially purified pool of enzyme had esterase activity against a series of short-chain alpha- and beta-naphthyl esters. The heterogeneity of salivary gland esterases, their relationship to PAF-acetylhydrolase, and the possible physiological functions of salivary gland PAF-acetylhydrolase activity are discussed.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1990

Serine esterases: structural conservation during animal evolution and variability in enzymatic properties in the genus Drosophila.

Both general esterases and acetylcholinesterases have been shown to be members of a homologous superfamily of serine esterases. A comparison of N-terminal sequences demonstrates that esterase-4 and -5 from Drosophila mojavensis belong to this family as well, with esterase-6 and esterase-P from D. melanogaster being the closest relatives. In order to investigate the presence of immunologically related esterases in other Drosophila species, crude larval extracts from five species were applied to two immunoaffinity columns with antibodies directed against esterase-4 and esterase-5 from D. mojavensis. The substrate preference for either 1- or 2-naphthyl acetate was determined. Both esterase-4 and esterase-5 from D. mojavensis are 'normally' specific for 2-naphthyl esters, but at least three of the cross-reacting esterases from the other species have a preference for 1-naphthyl esters. This difference in substrate preference is another example of the variability observed with Drosophila esterases.

Amino Acid Sequence↗
PubMed1994

Exon 11 of the rat cholesterol esterase gene encodes domains important for intracellular processing and bile salt-modulated activity of the protein.

The rat pancreatic cholesterol esterase is a 74,000 molecular weight protein encoded by a gene with 10 introns and 11 exons. The last exon of the cholesterol esterase gene is the largest and is also the least conserved exon among the cholesterol esterase genes of various species. The current study investigates the functional role of the exon 11 domain in rat cholesterol esterase. The transfection of native cholesterol esterase cDNA into COS cells resulted in an enzymatically active cholesterol esterase that was secreted by the cells. In contrast, transfection of cholesterol esterase cDNA with 88% of the exon 11 residues deleted from the sequence resulted in a protein that was not secreted by the cells. The cholesterol esterase with deletions in the exon 11 domain retained the ability to bind bile salt but was found to be enzymatically inactive. The inefficient secretion and the loss of enzyme activity for the truncated protein were not due to deletion of the proline-rich repeating units located in the exon 11 domain at the carboxyl terminus of the cholesterol esterase. The expression of rat cholesterol esterase with zero or one proline-rich units resulted in a truncated protein that was secreted by the transfected COS cells. The cholesterol esterases with reducing numbers of the proline-rich repeating units were also active in hydrolyzing p-nitrophenyl butyrate and cholesteryl oleate. The cholesterol esterase with fewer proline-rich repeating units were more active than the native enzyme in substrate hydrolysis at low bile salt concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

The effect of age and frailty upon blood esterase activities and their response to dietary supplementation.

1. The aims of this study were two-fold. First, to define ranges of blood esterase activities in three groups, namely young subjects, fit community dwelling elderly and frail, chronically hospitalised elderly subjects, and second, to determine whether low blood esterase activities in the frail patients could be altered by increasing their nutritional intake. 2. Plasma cholinesterase, aspirin esterase, paraoxonase and phenylacetate esterase activities were all significantly lower in the frail elderly compared with the young and fit elderly volunteers. The activity of red blood cell esterase was not different in the frail elderly. 3. Fourteen frail elderly patients were randomly assigned to receive either hospital meal provision plus supplemental feeding with Build-up (Nestle) and Maxijul (SHS Ltd) or hospital provision alone for 8 weeks. Dietary intake was measured for all patients at the start of the study and at week 8. Measurements of blood esterase (cholinesterase, phenylacetate esterase, paraoxonase, aspirin esterase and red blood cell esterase), albumin and anthropometric indices (weight, triceps skinfold thickness and mid arm circumference) were made before the study and repeated at week 4 and 8. 4. There was a significant increase in plasma cholinesterase at week 4 (P < 0.05) but this was not statistically significant at week 8. There were no significant changes in any of the other esterase activities or anthropometric measurements. 5. We conclude that the lower esterase activities of the frail chronically hospitalised elderly do not respond to dietary supplementation for a period of 8 weeks with routinely available products. The hypothesis that lower esterase activities are the direct result of undernutrition which would be corrected by dietary supplementation has not been supported by this study.

Aged↗
PubMed1979

Species difference and characterization of intestinal esterase on the hydrolizing activity of ester-type drugs.

The ability of the esterase from intestine was studied for hydrolysis of ester-type drugs during absorption. The intestinal esterase is present in the absorption sites in the intestine and hydrolyzes to a large extent during the absorption. In a study of the dietary effect on intestinal esterase, the esterase activity increased in rats fed a high-fat diet, decreased in those fasted or fed a fat-free diet, whereas the esterase activity in the rat treated with phenobarbital showed no marked change. Thus the esterase from intestinal mucosa appears to be characteristically quite different from hepatic esterase. The esterase from human intestine was characterized and compared with esterase from rats, mice, rabbits, guinea pigs and dogs. There was a difference in the substrate specificity of the esterase and there were significant species differences in the electrophoretic behavior of the enzyme among the species tested. These results indicate that intestinal esterase from humans differs characteristically from esterases in experimental animals.

Animals↗
PubMed2006

Evaluation of chiral alpha-cyanoesters as general fluorescent substrates for screening enantioselective esterases.

Esterases play a crucial role in industrial chemical synthesis, maintaining normal physiological metabolism and detoxifying exogenous ester-containing toxicants. To meet the rapidly increasing industrial need for all kinds of esterases, especially enantioselective esterases used to generate highly pure chiral compounds, general substrates are necessary for rapid screening, monitoring, purification, and characterization. In this study, general fluorescent substrates including phenolic derivatives and alpha-cyanoesters were evaluated for sensitivity in detecting esterases in buffer systems. Results with two different esterases and different incubation times suggested that the alpha-cyanoesters examined were significantly more sensitive at detecting esterases than the corresponding tested phenolic derivatives. More importantly, alpha-cyanoesters, containing a secondary alcohol, possess at least one chiral center; thus, they are tools to screen for enantioselective hydrolysis. Results indicated that the enantioselectivity of esterases toward general alpha-cyanoesters strongly depended on the esterase and the substrate, but the majority of esterases examined preferred S-isomers to their corresponding R-enantiomers. Most appealing was the very high enantioselectivity displayed in cytosolic esterases of the house fly. The potential utility of such esterases is discussed. In addition, the use of alpha-cyanoesters as chiral fluorescent substrates was demonstrated for monitoring in enantioselective esterases.

Animals↗
PubMed2001

Tissue localization of overproduced esterases in the mosquito Culex pipiens (Diptera: Culicidae).

We have investigated the tissue distribution of overproduced esterases A (A1 and A2) and B (B1 and B2) in strains of Culex pipiens L. by immunocytochemistry. S-LAB mosquitoes, lacking overproduced esterases, were used as reference. Tissues showing a strong specific reaction (fluorescence) were observed with anti-esterase A1 antiserum in S54 (with A1) and BOUAKE (with A2) strains, and with anti-esterase B1 antiserum in TEM-R and EDIT (with B1) and BOUAKE (with B2) strains. Overproduction of esterases A and B was tissue-specific. The most constant pattern for the two types of esterases was their overproduction in the alimentary canal and Malpighian tubes, although fluorescence varied in intensity depending on strains and developmental stages. There was no difference in the tissue distribution of esterases Al and A2. In contrast, esterases B pattern was highly variable among strains. Differences between TEM-R and EDIT were explained by the different overall overproduction and number of copies of the amplified gene (10-fold higher in TEM-R). The most striking difference in esterase B1 and B2 tissue localization concerned the nervous system where neurons were intenisely fluorescent in TEM-R and EDIT (B1), but not in BOUAKE (B2). All esterase B positive tissues in TEM-R contained large quantities of esterase B1 mRNA (in situ hybridization), indicating that at least part of the protein revealed by immunochemistry was produced in the tissues where it was observed. Our results are discussed in terms of the protection that the different esterases can confer during exposition to organophosphorous insecticides.

Animals↗
PubMed2003

Biochemical detection of esterases in the adult female integument of organophosphate-resistant Boophilus microplus (Acari: Ixodidae).

Esterase activity was present in the integument of adult female Boophilus microplus (Canestrini) ticks that are resistant to organophosphates (OP). Three esterases were purified from adult integument, which hydrolyze the substrates p-nitrophenylacetate and beta-naphthyl acetate after comparison of OP-resistant strain and an OP-susceptible strains. The esterases purified by ion-exchange chromatography were characterized using different esterase inhibitors; eserine sulfate, diethyl p-nitrophenyl phosphate (paraoxon), para-hydroxyl-mercuribenzoate (pHMB), and diisopropylphosphofluoridate (DFP). All of the esterases had a molecular mass of 64 Kd (PAGE), but were characterized based on the esterase inhibitor effects as a B-esterase with beta-naphthyl acetate affinity, a carboxylesterase with beta-naphthyl acetate and p-nitrophenyl acetate affinity, and one A-Esterase (nonspecific esterase) with p-nitrophenyl acetate affinity. The described esterases are an important detoxification mechanism in B. microplus ticks at the integument. We describe also a microplate biochemical assay for the detection of esterase activity in the tick integument, potentially a useful tool to detect esterase-mediated OP resistance in B. microplus ticks.

Animals↗
PubMed1987

"A" esterases and their role in regulating the toxicity of organophosphates.

Esterases which can hydrolyse organophosphates without being inhibited by them are termed "A" esterases. Using paraoxon and pirimiphos-methyl oxon as substrates, high "A" esterase activity is found in the liver and plasma or serum of a range of mammalian species. In a study of serum "A" esterases of sheep and humans, over 80% of the activity separated into the high density lipoprotein (HDL) fraction following ultracentrifugation. When HDL fractions from sheep serum were run on Sepharose gel columns, most of the paraoxonase activity separated as a single peak of estimated molecular weight 360,000, which corresponds to that of HDL2 of humans. During the course of purification of "A" esterases by three different column procedures, contrasting esterase elution profiles were obtained with organophosphate and pyrethroid substrates. This was strong evidence for the existence of multiple forms of HDL "A" esterases. Levels of "A" esterase activity in plasma and liver of birds were much lower than those of mammals. This appears to be the main reason why birds are much more susceptible than mammals to organophosphates such as pirimiphos-methyl and diazinon which form active oxons that are good substrates for mammalian "A" esterases. No "A" esterase was detected in strains of rust red flour beetle (Tribolium castaneum) which were resistant to organophosphates. Similar observations have been made with strains of other insects resistant to organophosphates, raising the question to what extent esterases of this type are present in insects.

Animals↗
PubMed1983

Alpha naphthyl acetate esterase in human blood cells with different molecular weights.

Normal human blood cells contain esterases which hydrolyze alpha-naphthyl acetate (alpha NA). Purified preparations of these cells were investigated by polyacrylamide gradient gel electrophoresis at pH 9.0 and subsequent staining of gels for esterase activity. Extractable alpha NA esterase was separated according to molecular weight. alpha NA esterase with molecular weight of 55 000 was observed only in lymphocytes and red cells. Lymphocytes from patients with B-cell chronic lymphocytic leukemia (B-CLL) showed alpha NA esterase with molecular weight of 45 000 instead of 55 000. Esterases with molecular weights of 60 000 and 70 000 were detected in granulocytes monocytes and red cells. Only platelets and red cells exhibited alpha NA esterase with molecular weight of 80 000. alpha NA esterases with molecular weight of 290 000 could be demonstrated in granulocytes and red cells. All blood cells contained esterase with molecular weight of 360 000. alpha NA esterase with molecular weight of 390 000 was detected only in red cells. In all blood cells (without lymphocytes) esterase with molecular weight of 500 000 was demonstrated. Only the enzyme in monocytes, granulocytes and red cells was sensitive to fluoride inhibition.

Blood Cells↗
PubMed1992

Specific induction by glucocorticoids of steroid esterase in rat hepatic microsomes and its release into serum.

Steroid esterase hydrolysing methylprednisolone 21-hemisuccinate was induced specifically and markedly in hepatic microsomes and serum of rats by various glucocorticoids. Among the glucocorticoids examined, dexamethasone and betamethasone showed the highest potency to induce the hepatic steroid esterase, the induction ratio being 32 and 33 times higher than the basal level (about 160 mU/g liver), respectively. Steroid esterase in the serum was induced greatly by fluocinolone acetonide and betamethasone to 92 and 79 times of the basal level of about 16 mU/mL, respectively, followed by dexamethasone and methylprednisolone. When dexamethasone was given to rats, the enzyme in other tissues except for duodenum and small intestine (of which activity was lowered to 50% of the basal level) was also elevated, but the induction ratio was much lower than that in the liver and serum. The induction of the steroid esterase is probably due to stimulation of de novo synthesis of the enzyme by glucocorticoids, because the elevation of esterase activity was inhibited by treatment with cycloheximide (a translation inhibitor) and actinomycin D (a transcription inhibitor), and about 4- and 10-hr lag time was observed before the elevation of esterase activity in liver and serum, respectively. Coupled with these observations the following results indicate that the steroid esterase in serum is probably synthesized in the liver and subsequently released into the blood via the Golgi apparatus: (1) when the liver of rats treated with dexamethasone was subjected to perfusion with a recycling system, significant amounts of steroid esterase were released into the perfusate; (2) anti-hepatic esterase antibody inhibited the steroid esterase activity not only in the liver but also in serum; and (3) monensin, which prevents the secretion of various kinds of secretory proteins by disrupting the function of the Golgi apparatus, inhibited the elevation of the steroid esterase activity in serum by dexamethasone but did not affect the induction in liver.

Animals↗
PubMed1995

Characterization of a salivary gland-specific esterase in the vector mosquito, Aedes aegypti.

Esterase enzymatic activity was investigated in salivary gland lysates of adult Aedes aegypti. Esterases in lysates made from female glands had higher specific activity than those in lysates from male glands towards beta-naphthyl acetate but showed no difference with alpha-naphthyl butyrate as a substrate. Female salivary gland lysates showed no difference in activity to alpha- and beta-forms of naphthyl acetate and no discernable activity towards alpha-naphthyl caprate. Both female and male salivary gland lysates exhibited phosphatase enzymatic activity but the specific activities were lower than those seen for the esterase enzymatic activity. Salivary gland esterase activity was inhibited completely by paraoxon, para-hydroxymercurobenzoate, tetraethylammonium iodide and moderately by diisopropylfluorophosphate. Eserine and phenylmethylsulfonylfluoride had no effect on enzyme activity. In a probing assay, adults of both sexes were shown to secrete esterase in saliva. Esterase activity was present in the saliva of females probing for either a sugar meal or a blood meal. Furthermore, esterase was secreted from female salivary glands in culture. Histochemical analysis of dissected salivary glands showed that the majority of the esterase enzymatic activity was in the distal-lateral lobes of the female tissues, although the proximal-lateral and medial lobes also had activity. Male salivary glands stained uniformly over all of the lobes. A salivary gland-specific esterase, designated SG-EST, appears to account for the majority of enzyme activity in the glands. SG-EST was partially purified by electroelution of an active protein from native polyacrylamide gels, and has an approximate molecular weight of 65,000 Da. In separate experiments, affinity chromatography independently identified a single 65,000 Da protein likely to be SG-EST. Native electrophoretic analysis of salivary glands revealed that, while most enzyme activity is due to SG-EST, there are two other esterases present. One of these minor moieties is present in adult tissues in addition to the salivary gland, and the other is present throughout development. Possible functions of the salivary gland esterase are discussed.

Aedes↗
PubMed2004

Enhanced esterase gene expression and activity in a malathion-resistant strain of the tarnished plant bug, Lygus lineolaris.

Extensive use of insecticides on cotton in the mid-South has prompted resistance development in the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). A field population of tarnished plant bugs in Mississippi with 11-fold higher resistance to malathion was used to examine how gene regulation conferred resistance to this organophosphate insecticide. In laboratory bioassays, synergism by the esterase inhibitors S,S,S,-tributylphosphorotrithioate (DEF) and triphenylphosphate (TPP) effectively abolished resistance and increased malathion toxicity by more than 80%. Esterase activities were compared in vitro between malathion susceptible and resistant (selected) strains. More than 6-, 3- and 10-fold higher activities were obtained with the resistant strain using alpha-naphthyl acetate, beta-naphthyl acetate, and p-nitrophenyl acetate, respectively. Up to 95% and 89% of the esterase activity in the susceptible and resistant strains, respectively, was inhibited by 1 mM DEF. Inhibition of esterase activity up to 75% and 85% in the susceptible and resistant strains, respectively, was obtained with 0.03 mM TPP. Esterase activities in field populations increased by up to 5.4-fold during the fall season. The increase was synchronized with movement of the insect into cotton where exposure to pesticides occurred. Esterase cDNA was cloned and sequenced from both malathion susceptible and resistant strains. The 1818-nucleotide cDNA contained a 1710-bp open reading frame coding a 570 amino acid protein which was similar to many insect esterases conferring organophosphate resistance. No amino acid substitution was observed between susceptible and resistant strains, indicating that esterase gene mutation was not involved in resistance development in the resistant strain in Mississippi. Further examination of esterase gene expression levels using quantitative RT-PCR revealed that the resistant strain had a 5.1-fold higher level of esterase mRNA than the susceptible strain. The results of this study indicated that up-regulation of the esterase gene appeared to be related to the development of resistance in the tarnished plant bug.

Amino Acid Sequence↗
PubMed1975

Esterase zymograms of Proteus and Providencia.

The intracellular esterases of 80 strains of Proteus and Providencia were analysed by the acrylamide-agarose zymogram technique using several synthetic substrates. The esterase bands were classified in five main groups. The alphaA-esterase bands hydrolysed alpha-naphthyl acetate and were resistant or relatively insensitive to di-isofluoropropyl phosphate (DFP). The alphaB-esterase band hydrolysed both alpha-naphthyl acetate and alpha-naphthyl butyrate and were very sensitive to DFP. Both groups of esterase bands were inactivated by heat. The betaA- and betaB-esterase bands hydrolysed beta-naphthyl acetate and were sensitive to DFP; these were distinguishable by the difference in their relative activity towards beta-naphthyl butyrate and in their relative stability to heat. The alpha-beta-esterase bands hydrolysed alpha- and beta-naphthyl acetates and alpha- and beta-naphthyl butyrates; they were inactivated by heat and were sensitive to DFP. The distribution of these esterase bands among the strains of Proteus and Providencia and their electrophoretic patterns established esterase profile types which correlate with the classification based on traditional bacteriological tests. The degree of inter-strain similarity in esterase pattern varied highly among species. The homogeneity of Proteus mirabilis and especially of Providencia stuartii contrasted with the heterogeneity of other species. This disparity suggests that the bacteria of the tribe Proteae have not the same degree of intra-specific differentiation in physico-chemical properties of esterases.

Butyrates↗