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PubMed2000

Feruloyl esterase activity of the Clostridium thermocellum cellulosome can be attributed to previously unknown domains of XynY and XynZ.

The cellulosome of Clostridium thermocellum is a multiprotein complex with endo- and exocellulase, xylanase, beta-glucanase, and acetyl xylan esterase activities. XynY and XynZ, components of the cellulosome, are composed of several domains including xylanase domains and domains of unknown function (UDs). Database searches revealed that the C- and N-terminal UDs of XynY and XynZ, respectively, have sequence homology with the sequence of a feruloyl esterase of strain PC-2 of the anaerobic fungus Orpinomyces. Purified cellulosomes from C. thermocellum were found to hydrolyze FAXX (O-(5-O-[(E)-feruloyl]-alpha-L-arabinofuranosyl)-(1-->3)-O-beta-D- xyl opyranosyl-(1-->4)-D-xylopyranose) and FAX(3) (5-O-[(E)-feruloyl]-[O-beta-D-xylopyranosyl-(1-->2)]-O-alpha-L- arabinofuranosyl-[1-->3])-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose) , yielding ferulic acid as a product, indicating that they have feruloyl esterase activity. Nucleotide sequences corresponding to the UDs of XynY and XynZ were cloned into Escherichia coli, and the expressed proteins hydrolyzed FAXX and FAX(3). The recombinant feruloyl esterase domain of XynZ alone (FAE(XynZ)) and with the adjacent cellulose binding domain (FAE-CBD(XynZ)) were characterized. FAE-CBD(XynZ) had a molecular mass of 45 kDa that corresponded to the expected product of the 1,203-bp gene. K(m) and V(max) values for FAX(3) were 5 mM and 12.5 U/mg, respectively, at pH 6.0 and 60 degrees C. PAX(3), a substrate similar to FAX(3) but with a p-coumaroyl group instead of a feruloyl moiety was hydrolyzed at a rate 10 times slower. The recombinant enzyme was active between pH 3 to 10 with an optimum between pH 4 to 7 and at temperatures up to 70 degrees C. Treatment of Coastal Bermuda grass with the enzyme released mainly ferulic acid and a lower amount of p-coumaric acid. FAE(XynZ) had similar properties. Removal of the 40 C-terminal amino acids, residues 247 to 286, of FAE(XynZ) resulted in protein without activity. Feruloyl esterases are believed to aid in a release of lignin from hemicellulose and may be involved in lignin solubilization. The presence of feruloyl esterase in the C. thermocellum cellulosome together with its other hydrolytic activities demonstrates a powerful enzymatic potential of this organelle in plant cell wall decomposition.

Amino Acid Sequence↗
PubMed1999

The hemagglutinin-esterase of mouse hepatitis virus strain S is a sialate-4-O-acetylesterase.

By comparative analysis of the hemagglutinin-esterase (HE) protein of mouse hepatitis virus strain S (MHV-S) and the HE protein of influenza C virus, we found major differences in substrate specificities. In striking contrast to the influenza C virus enzyme, the MHV-S esterase was unable to release acetate from bovine submandibulary gland mucin. Furthermore, MHV-S could not remove influenza C virus receptors from erythrocytes. Analysis with free sialic acid derivatives revealed that the MHV-S HE protein specifically de-O-acetylates 5-N-acetyl-4-O-acetyl sialic acid (Neu4, 5Ac2) but not 5-N-acetyl-9-O-acetyl sialic acid (Neu5,9Ac2), which is the major substrate for esterases of influenza C virus and bovine coronaviruses. In addition, the MHV-S esterase converted glycosidically bound Neu4,5Ac2 of guinea pig serum glycoproteins to Neu5Ac. By expression of the MHV esterase with recombinant vaccinia virus and incubation with guinea pig serum, we demonstrated that the viral HE possesses sialate-4-O-acetylesterase activity. In addition to observed enzymatic activity, MHV-S exhibited affinity to guinea pig and horse serum glycoproteins. Binding required sialate-4-O-acetyl groups and was abolished by chemical de-O-acetylation. Since Neu4,5Ac2 has not been identified in mice, the nature of potential substrates and/or secondary receptors for MHV-S in the natural host remains to be determined. The esterase of MHV-S is the first example of a viral enzyme with high specificity and affinity toward 4-O-acetylated sialic acids.

Acetylation↗
PubMed2005

Characteristics of adjacent family 6 acetylxylan esterases from Fibrobacter succinogenes and the interaction with the Xyn10E xylanase in hydrolysis of acetylated xylan.

Acetylxylan esterase genes axe6A and axe6B located adjacent to one another on a Fibrobacter succinogenes chromosome have been separately cloned and their properties characterized. The corresponding esterases contained an N-terminal carbohydrate esterase family 6 catalytic domain (CD) and a C-terminal family 6 carbohydrate-binding module (CBM). The amino acid sequences of the CDs and CBMs were found to exhibit 52% and 40% amino acid similarity, respectively. The CDs of the two esterases exhibited the highest similarity to CDs of acetylxylan esterases: AxeA from the ruminal fungi Orpinomyces sp. and BnaA from Neocallimastix patriciarum. Axe6A and Axe6B were optimally active at neutral pH and had low K(m) values of 0.084 and 0.056 mmol x L(-1), respectively. Axe6A and Axe6B were shown to bind to insoluble cellulose and xylan and to soluble arabinoxylan. Axe6A deacetylated acetylated xylan at the same initial rate in the presence and absence of added Xyn10E xylanase from F. succinogenes, but the action of the xylanase on acetylated xylan was dependent upon the initial activity of Axe6A. The capacity of acetylxylan esterases to bind to plant cell wall polymers and to independently deacetylate xylan enabling xylanase to release xylooligo saccharides, documents the central role these enzymes have to improve access of F. succinogenes to cellulose.

Acetylation↗
PubMedDate not supplied

Proteins binding to kallikrein and esterase A2 in the urine of salt-sensitive and salt-resistant rats.

Iodine-labeled ([125I]) rat urinary kallikrein and rat urinary TAME esterase A2 were used as probes to look for urinary and plasma proteins that bind to these enzymes. Such proteins are presumptive enzyme inhibitors. Complexes formed with labeled enzymes were identified by polyacrylamide gel electrophoresis followed by autoradiography. Urine from young (6 weeks old) Dahl salt-sensitive (S) rats showed no, or only traces, of protein binding to kallikrein. Concomitant with the slow development of hypertension and proteinuria in S rats fed normal rat chow, one of the six kallikrein-binding proteins demonstrable in plasma was readily found in S-rat urine. This kallikrein-binding protein was called "KBP-1." R rats showed either no or much less KBP-1 in the urine, compared to S rats up to 5 months of age. A partly purified preparation of KBP-1 was shown to inhibit the TAME esterase activity of rat urinary kallikrein in the radiometric TAME assay. Urine of proteinuric S rats also contained two TAME esterase-binding proteins, TEBP-1 and TEBP-2, detected with the [125I]-esterase A2 probe. As S rats aged from 3 to 8 months, free KBP-1 disappeared from the urine in spite of increased and marked proteinuria and the continued presence of KBP-1 in plasma. Concomitant with this age-related loss of urinary KBP-1 there was a marked shift in S urinary proteins binding to [125I]-esterase A2 from TEBP-1 to TEBP-2. It was speculated that KBP-1 and TEBP-1 were the same protein detectable with either labeled kallikrein or labeled esterase A2. The concomitant disappearance of free KBP-1 (TEBP-1) and the appearance of free TEBP-2 in the urine of old, hypertensive, proteinuric S rats suggests that: 1) most of the KBP-1 (TEBP-1) is bound to enzyme(s) in old rats; or 2) KBP-1 (TEBP-1) is largely converted to TEBP-2 in old rats; or 3) both are true and that binding of KBP-1 (TEBP-1) to enzymes is associated with the generation of TEBP-2.

Animals↗
PubMed2003

The molecular chaperone, alpha-crystallin, protects against loss of antigenicity and activity of esterase caused by sugars, sugar phosphate and a steroid.

Previously we showed that glycation-induced inactivation and loss of antigenicity of enzymes occur simultaneously. Alpha-crystallin, a major structural protein of the mammalian lens, prevents the aggregation of other proteins and protects enzyme function against post-translational modification in vitro. However, it is not known whether alpha-crystallin can also protect against loss of antigenicity of enzymes. Esterase activity in the lens is decreased in senile cataract and diabetes. We investigated the loss of antigenicity of esterase caused by different insults and the ability of alpha-crystallin to protect. Inactivation of carboxylesterase by sugars, fructose 6-phosphate (F6P) and a steroid, prednisolone-21-hemisuccinate (P-21-H), was measured spectrophotometrically in the presence and absence of alpha-crystallin, while loss of antigenicity was monitored simultaneously using an immunoprecipitation method. The esterase was progressively inactivated by fructose, F6P, ribose, and P-21-H. Bovine alpha-crystallin fully protected against inactivation of esterase by all four compounds, and also protected against loss of antigenicity of the esterase by fructose, ribose and P-21-H at a molar ratio of 1:1. The results indicated that alpha-crystallin, under our experimental conditions, clearly exhibited the ability to prevent loss of antigenicity and inactivation of esterase. The protective effect of alpha-crystallin against loss of antigenicity indicates a novel aspect of its chaperoning function.

Animals↗
PubMed1980

A kinetic test for the assay of the C1 esterase-inhibitor.

The most satisfactory diagnostic procedure for hereditary angioneurotic oedema is the demonstration of low serum levels of C1 esterase-inhibitor. A modified method for the assay of this protein is described. It is based on the kinetic measurement of the C1 esterase-inhibitor when it inhibits the hydrolysis of N-acetyl-L-tyrosine-ethyl ester by C1 esterase. The relative C1 esterase-inhibitor concentration is based on the initial hydrolytic velocity, which can be evaluated from the pH change in a short time and within a small range. High reproducibility, cheap instrumentation and short time of analysis are some of the favorable aspects of this method in comparison with the 'end point titrimetric' method. Furthermore, this paper describes the mechanism of inhibition of C1 esterase by C1 esterase-inhibitor. The results are indicative of a non-competitive mechanism. The value of the Michaelis-Menten constant, Km, is 0.017 +/- 0.001 mol/l at 37 degrees C, in the optimum pH range 7.2-7.4. An estimate of KI in arbitrary units is also given.

Angioedema↗
PubMed2000

[TAME]-esterase--a new cardiovascular risk factor in smokers.

A mathematical model has been proposed to study the effect of [TAME] esterase on blood clotting time. Using this model, clotting time was found to decrease by 30% with increasing plasma [TAME] esterase activity in a group of smokers. It is hypothesized that [TAME] esterase through its effect on Hageman factor could affect clotting time. However mechanism of clotting by [TAME] esterase remains to be elucidated. It is concluded that [TAME] esterase is involved in the cascade of reactions leading to blood coagulation and increased [TAME] esterase activity could be an additional risk factor for possible cerebro-vascular accidents in smokers.

Adult↗
PubMed1991

Characterization of Pseudomonas fluorescens carboxylesterase: cloning and expression of the esterase gene in Escherichia coli.

The Pseudomonas fluorescens gene (estB) that encodes a novel esterase (esterase II) was cloned into Escherichia coli JM83. DNA sequencing found a single open reading frame of 654 nucleotides. The open reading frame was confirmed by N-terminal amino acid sequence analysis of the esterase protein. A potential Shine-Dalgarno sequence is followed by the coding sequence of the estB gene. The amino acid sequence deduced from the nucleotide sequence contains the consensus active site sequence, G-X-S-X-G, of serine esterases. The enzyme expressed in an E. coli clone was purified by ion-exchange chromatography and gel filtration. Homogeneity of the purified enzyme was confirmed using SDS-polyacrylamide gel electrophoresis. The native enzyme exists as a dimer consisting of two identical subunits, each with a molecular weight of 23,000. The results of the experiments for identifying substrate specificity and the inhibitor studies suggest that this enzyme is a carboxylesterase (EC 3.1.1.1) and a serine residue is present at the active site of the esterase, as in the esterases of animal tissues.

Amino Acid Sequence↗
PubMed1991

Histochemical and biochemical studies on esterase activity in the rat ovary.

A correlative histochemical and biochemical study has been made of the changes in esterase positive sites in immature (10-, 20- and 30-days old), mature normal cycling (3-, 5- and 8-months-old), pregnant and lactating rat ovaries. The typical perivascular esterase-positive sites localized in the hilar portion, branch along the blood vessels and traverse into medullary and cortical portions of the ovary. The stromal vascularity surrounding the normal developing follicles, corpora lutea, atretic follicles and interstitial gland tissue showed rich activity of this enzyme system. On semiquantitative basis the number, intensity and quantity of esterase-positive sites vary with the maturation and reproductive states of the rat. The administration of estradiol-17 beta increased the fine perifollicular and theca externa perivascular esterase-positive sites, whereas atropine and reserpine affected severely both the large and fine meshwork of esterase-positive sites. Biochemical estimates of acetylcholine esterase activity endorse these histochemical observations. The possible roles of AChE activity in varied ovarian functions are discussed.

Acetylcholinesterase↗
PubMed1985

Human plasma carboxyl esterase-catalyzed triolein hydrolysis. Existence of promoting factor in serum.

The possibility that some factor in serum changes the substrate specificity of purified human plasma carboxyl esterase, which hydrolyzes the short chain fatty acid ester, tributyrin, was investigated. The purified carboxyl esterase from human plasma hydrolyzed 48 mmol of tributyrin/mg of protein/h, monoolein at 1560 mumol of released fatty acids/mg of protein/h, diolein at 133 mumol of released fatty acids/mg of protein/h, and triolein at less than 10 mumol of released fatty acids/mg of protein/h. When human serum was applied to phenyl-Sepharose, a triolein hydrolysis-promoting factor (THPF) for purified carboxyl esterase was bound to the gel and was eluted with water. This partially purified human serum THPF enhanced carboxyl esterase-catalyzed triolein hydrolysis about 30-fold, diolein hydrolysis 2-fold, and monoolein hydrolysis 1.5-fold. Hydrolysis of triolein in very low density lipoproteins (d less than 1.006) and intermediate lipoproteins (1.006 less than d less than 1.019) by carboxyl esterase was also enhanced by addition of THPF. THPF activity was reduced by treatment of delipidation, but resistant to trypsin treatment or heating at 50 degrees C. These results indicated that serum carboxyl esterase can hydrolyze the long chain fatty acid ester, triolein, in the presence of triolein hydrolysis-promoting factor in serum.

Carboxylic Ester Hydrolases↗
PubMed1980

Irreversible phosphorylation of brain neurotoxic esterase. The primary event leading to the delayed neuropathy caused by some organophosphorus esters.

Organophosphorus compounds which cause delayed neurotoxic effects phosphorylate a characteristic nervous-tissue protein and inhibit its activity as an esterase. Studies with a variety of inhibitors reveal that the toxic effect does not occur because of the loss of esterase activity but depends on the chemistry of the inhibited enzyme. A process analogous to the 'aging' of inhibited cholinesterase occurs after neurotoxic esterase has been inhibited by neurotoxic agents which leaves a charged acidic group attached to the membrane-bound esterase. This charge could disrupt normal metabolism in the neurone. Protective compounds inhibit neurotoxic esterase but the 'aging' process cannot occur, so that there is no formation of a charged group. Neurotoxic esterase occurs widely in the brain. Attempts are being made to locate the enzyme intraneuronally. The present understanding is of great value in toxicology. However, it has not yet clarified the physiological processes which maintain long axons in normal health.

Animals↗
PubMed1981

Studies on the in vivo absorption of micellar solutions of tocopherol and tocopheryl acetate in the rat: demonstration and partial characterization of a mucosal esterase localized to the endoplasmic reticulum of the enterocyte.

The in vivo absorption of alpha-tocopherol from micellar solubilized solutions of free alpha-tocopherol and alpha-tocopheryl acetate was investigated using isolated loops of rat jejunum and found to be similar. Although analysis of the fluid remaining in the loop following the absorptive period with tocopheryl acetate showed that esterase activity and free tocopherol were present, calculations suggested that luminal hydrolysis of the ester could not have accounted for the similar rates of absorption of the free and esterified tocopherols. A mucosal source of the esterase activity was postulated and subsequently identified and characterized with respect to pH optimum, enzyme kinetics, and activation by bile salts, and shown to be distinct from pancreatic esterase. Analytical subcellular fractionation studies on homogenates of isolated jejunal enterocytes demonstrated that esterase activity against both p-nitrophenyl acetate and tocopheryl acetate was localized to the endoplasmic reticulum. These studies suggest that although the bulk of tocopheryl esters are normally hydrolyzed in the intestinal lumen by pancreatic esterase prior to uptake, some of the esters may be hydrolyzed intraluminally by the mucosal enzyme and some taken up intact by the jejunal mucosa and hydrolyzed intracellularly. This mucosal esterase may be of particular importance in conditions of pancreatic insufficiency.

Acetylesterase↗
PubMed1985

The use of 2-thionaphthyl acetate as a substrate for the localization and characterization of nonspecific esterase activity in rat alveolar and peritoneal macrophages.

A 2-thionaphthyl acetate substrate was utilized to assess the subcellular distribution of nonspecific esterases in rat pulmonary alveolar and peritoneal macrophages. The enzymatically liberated 2-thionaphthol was visualized at pH 7.1 by utilizing gold as a capture agent. Glutaraldehyde-fixed macrophages derived from healthy animals using standard lavage techniques exhibited a high affinity for the substrate and reaction times were thus relatively short (30-60 min). Alveolar macrophages had heavy reaction product on the external surface of the plasma membrane and membranes limiting cisternae of rough endoplasmic reticulum, Golgi complex and mitochondria. Only a thin layer of reaction density was observed associated with the limiting membranes of lysosomes and phagosomes. Peritoneal macrophages were similarly but much less intensely reactive, although they generally lacked or had very little plasma membrane-associated staining. The 2-thionaphthyl acetate esterase activities in both alveolar and peritoneal macrophages were sensitive to diisopropylfluorophosphate (DFP), while only the latter was inhibited by sodium fluoride. Polyacrylamide gel isoelectric focusing of whole cell homogenates indicated that the 2-thionaphthyl acetate esterase activity was the same as that for alpha-naphthyl acetate in these cells. The data indicate that a significantly different distribution of nonspecific esterase activity results with use of a 2-thionaphthyl acetate substrate in the presence of gold ions than that previously reported with other methods. The rapid penetrability and sensitivity of this substrate make it a potentially useful tool for evaluating subcellular localization of esterase activity and probing characteristics of cellular organelles.

Animals↗
PubMed1978

Localization of kallikrein and its relation to other trypsin-like esterases in the rat pancreas. A comparison with the submandibular gland.

Kallikrein was located by the direct immunofluorescence technique to the granule-containing luminal portion of pancreatic acinar cells. For the demonstration of the intracellular distribution of pancreas kallikrein, in vivo fixation of the gland was necessary. No kallikrein was found in the duct cells or in the islets of Langerhans. Quantitation by single radial immunodiffusion showed that the concentration of kallikrein in the presence was 1.32 +/- 51 microgram/g wet weight, i.e. 1/91 that of the rat submandibular gland. Bz-Arg-OEt-esterases were in the pancreas found as pro-enzyme but as active enzyme in the submandibular gland. Trypsin-like esterases, hydrolyzing epsilon-amino caproic acid naphtol-AS-D.HBr (ACA), were found in the active form in both submandibular gland and pancreatic homogenates. The submandibular gland contained per g wet weight 6 times as much ACA-esterase activity as the pancreas. In the submandibular gland, kallikrein and ACA-esterase activity were found together in practically all granular tubular cells. Thus, the granular tubular cell contains kallikrein as well as other trypsin-like enzymes like the ACA-esterase, and is in this way comparable to the pancreatic acinar cell. An extraglandular function of kallikrein is suggested for the pancreas in contrast to other kallikrein-containing exocrine organs.

Animals↗
PubMed2005

Immunological assessment of an insecticide resistance-associated esterase in the Western corn rootworm.

In previous investigations, we have determined that organophosphate resistance in the western corn rootworm, Diabrotica virgifera virgifera, is at least partially attributed to a group of non-specific carboxylesterases referred to as group II. Antiserum raised against a purified 66-kDa group II esterase is specific for the denatured enzyme. This antiserum reacts similarly with both beetle homogenates from resistant and susceptible populations, although there is much higher signal intensity in immunoblots of resistant relative to susceptible beetles. These results suggest that overproduction of group II esterases is the underlying basis of esterase-mediated resistance in D. v. virgifera by demonstrating that (1) group II esterases are immunologically indistinguishable between the resistant and susceptible populations, and (2) the intensity differences are due to increased group II esterase proteins in the resistant population. The diagnostic potential of immunological-based assays was tested with a traditional diagnostic concentration bioassay and a biochemical-based native PAGE assay. Significant correlations were observed among all three diagnostic assays (regression coefficients ranging from 0.95 to 0.96). These results demonstrate the importance of the 66-kDa protein as a resistance-associated biochemical marker, thus emphasizing the potential for 66-kDa protein-targeted immunoassays in resistance monitoring programs.

Animals↗
PubMedDate not supplied

Esterase distribution in the rabbit cornea and its implications in ocular drug bioavailability.

Being the major pathway by which topically applied ophthalmic drugs enter the eye, the cornea can control the amount of active drug ultimately absorbed by offering resistance to drug permeation and by metabolizing the drug during permeation. This research seeks to determine the esterase activity in the cornea and two of its component layers--epithelium and stroma-endothelium--so as to anticipate the extent to which drugs containing ester linkages will be metabolized during transport. This has been achieved by incubating corneal homogenates of albino and pigmented rabbits of various age groups with alpha-naphthyl acetate, the model substrate, and monitoring the fluorescence intensity due to alpha-naphthol as a function of time. The results indicate that: (1) esterase activity in the epithelium is approximately twice that in the stroma-endothelium; (2) esterase activity in the intact cornea is linearly related to those in the epithelium and the stroma-endothelium; and (3) the esterase activity in the cornea and its component layers varies with rabbit's age and strain. According to these results the bulk of esterase-mediated hydrolysis is expected to take place in the epithelium, so that the residence time of a drug in this tissue can have a significant impact on its ocular bioavailability.

Animals↗
PubMed2006

Cloning and expression of a Melanocarpus albomyces steryl esterase gene in Pichia pastoris and Trichoderma reesei.

The ste1 gene encoding a steryl esterase was isolated from the thermophilic fungus Melanocarpus albomyces. The gene has one intron, and it encodes a protein consisting of 576 amino acids. The deduced amino acid sequence of the steryl esterase was shown to be related to lipases and other esterases such as carboxylesterases. Formation of mature protein requires post-translational removal of a putative 18-amino-acid signal sequence and a 13-residue propeptide at the N-terminus. The intronless version of the Melanocarpus albomyces ste1 gene was expressed in Pichia pastoris under the inducible AOX1 promoter. The production level was low, and a large proportion of the total activity yield was found to be present intracellularly. However, the fact that steryl esterase activity was produced by P. pastoris cells carrying the expression cassette confirmed that the correct gene had been cloned. The ste1 gene was subsequently expressed in T. reesei under the inducible cbh1 promoter, and a clearly higher production level was obtained. About 60% of the total activity was bound to the fungal mycelium or to solid components of the culture medium, or existed as aggregates. Triton X-100 was successfully used to recover this activity. The heterologous production system in T. reesei provides a means of producing M. albomyces steryl esterase STE1 reliably in large scale for future studies.

Amino Acid Sequence↗
PubMed1995

Direct evaluation of stereoselectivity of cancer esterases by polyacrylamide gel electrophoresis coupled with activity staining with chiral naphthyl esters.

Both enantiomers of alpha-naphthyl 2-phenylpropanoate (PhPr(ONap)), N-acetylalaninate (AcAla(ONap)), N-methoxycarbonylalaninate (MocAla(ONap)), N-methoxycarbonylvalinate (MocVal(ONap)), N-acetylprolinate (AcPro(ONap)), and N-(trifluoroacetyl)prolinate (TfaPro(ONap)) were prepared and used with Fast Blue RR salt for activity staining of esterases separated by polyacrylamide gel electrophoresis. Comparison of the band thicknesses stained with each enantiomer indicates stereoselectivity of the major esterase in that band. Several esterases in normal rat liver, rat hepatoma-derived cells, and mouse B16 melanoma showed alteration or inversion of stereoselectivity by the substrate change from MocAla(ONap) to MocVal(ONap) or from AcPro(ONap) to TfaPro(ONap). The stereoselectivity of the major esterases for MocVal(ONap) was reversed between the murine liver and the B16 melanoma enzymes. The present staining with chiral naphthyl esters is very effective for surveying rapidly the stereoselectivity of animal tissue and cancer esterases.

Animals↗