Pectin methyl esterase from orange fruit: characterization and localization by in-situ hybridization and immunohistochemistry

Pectin methyl esterase (PME) from orange (Citrus sinensis L.) fruit peels has been purified by ammonium sulphate precipitation, and ion-exchange and gel-filtration chromatography. Characterization of the enzyme revealed a 36-kDa protein with an isoelectric point >9, a pH optimum at 7 and temperature optimum at 50 °C. The substrate specificity and kinetic experiments showed that the affinity of PME for pectin was highly dependent on the degree of esterification (DE) of the pectin, with K _m values of 0.7 mg ml^-1 for pectin with a DE of 70% and 17 mg ml^-1 for pectin with a DE of 25%. The sequences of the NH₂-terminal end of digested peptides from the mature protein were obtained. A DNA fragment of 501 bp was cloned by polymerase chain reaction amplification using degenerate primers and was further used for screening of a cDNA library. Two cDNA clones were isolated encoding PMEs of 584 amino acids and 362 amino acids, respectively, including a putative signal peptide. The deduced amino acid sequence showed full identity to the sequenced peptides. Polyclonal antibodies raised against orange peel PME were used for immunohistochemistry. The main localization of PMEs was in the outer cell layers of the juice vesicles, in the outer cell layers of the lamellae between the segments and in the inner cell layers of the albedo in the peel. In-situ hybridization showed that the mRNA is very abundant in the fruit and was found in the same cell layers as the native enzyme. A very intensive staining for PME mRNA was also seen in the core and in the flavedo close to the oil glands. Received: 15 November 1997 / Accepted: 7 April 1998     

Acetyl esterase from mediterranean oranges: partial purification, immobilisation and biotransformations

Acetyl esterase (acetic-ester acetylhydrolase, EC 3.1.1.6) from citrus peel, whose natural role is not well known, catalyses, in vitro, the hydrolysis of acetyl groups from a wide range of substrates. This enzyme was extracted from Mediterranean orange peel, largely available in Italy, and purified 190-fold by a single chromatographic step on Sepabeads FP-HG. SDS polyacrylamide gel electrophoresis of the purified enzyme showed a major protein band, corresponding to a molecular mass of 45 kDa. Both free and immobilised enzyme were used in biotransformations. The enzyme removed the acetyl group in the 3 position of β-lactamic antibiotics, such as cephalosporin C and the intermediate 7-aminocephalosporanic acid with ≥98% conversion and 91-93% product yield.     

Purification, characterization and mass spectrometric sequencing of a thermophilic glucuronoyl esterase from Sporotrichum thermophile

The cellulolytic system of the thermophilic fungus Sporotrichum thermophile contains a recently discovered esterase that may hydrolyze the ester linkage between the 4- O -methyl- d -glucuronic acid of glucuronoxylan and lignin alcohols. The glucuronoyl esterase named St GE1 was purified to homogeneity with a molecular mass of M _r 58 kDa and pI 6.7. The enzyme activity was optimal at pH 6.0 and 60 °C. The esterase displayed a narrow pH range stability at pH 8.0 and retained 50% of its activity after 430 and 286 min at 50 and 55 °C, respectively. The enzyme was active on substrates containing glucuronic acid methyl ester, showing a lower catalytic efficiency on 4-nitrophenyl 2- O -(methyl-4- O -methyl-α- d -glucopyranosyluronate)-β- d -xylopyranoside than its mesophilic counterparts reported in the literature, which is typical of thermophilic enzymes. St GE1 was proved to be a modular enzyme containing a noncatalytic carbohydrate-binding module. LC-MS/MS analysis provided peptide mass and sequence information that facilitated the identification and classification of St GE1 as a family 15 glucuronoyl esterase that showed the highest homology with the hypothetical glucuronoyl esterase CHGG_10774 of Chaetomium globosum CBS 148.51. This work represents the first example of the purification and identification of a thermophilic glucuronoyl esterase from S. thermophile .     

Rapid and simple assay for feruloyl and p-coumaroyl esterases

A rapid, simple and sensitive method for detection of ferulic and p-coumaric acids using HPLC has been developed which can be used to determine the respective phenolic acid esterase activities of microorganisms. Prior concentration, purification or derivatization of the samples are not required. As little as 0.5 mg ferulic or p-coumaric acid/I could be detected and estimated in < 1 h. The method is specific for the two phenolic acids sice no interference by other components was observed.The authors are with the Department of Microbiology and Biochemistry, University of the Orange Free State (UOFS), PO Box 339, Bloemfontein 93000, South Africa     

The use of electrophoresis in the separation of two closely related species of terrestrial slugs

The pattern of variation of non-specific esterases, revealed by the use of disc electrophoresis, was used in an investigation of the specific difference between Limax flavus and L. pseudoflavus. The isozyme patterns were used to differentiate between the two taxa both qualitatively and quantitatively. The results were in agreement with the results from studies of the variation in the morphology of the distal portions of the genitalia and of external body colouration and patterning. The biochemical methods allowed a rapid estimation of the difference between the two taxa and were more precise than the use of colour variation.     

Characterization of a novel cold active and salt tolerant esterase from Zunongwangia profunda

A novel cold active esterase, EstLiu was cloned from the marine bacterium Zunongwangia profunda, overexpressed in E. coli BL21 (DE3) and purified by glutathione-S transferase (GST) affinity chromatography. The mature esterase EstLiu sequence encodes a protein of 273 amino acids residues, with a predicted molecular weight of 30 KDa and containing the classical pentapeptidase motif from position 156 to 160 with the catalytic triad Ser158-Asp211-His243. Although, EstLiu showed 64% similarity with the hypothetical esterase from Chryseobacterium sp. StRB126 (WP_045498424), phylogenetic analysis showed it had no similarity with any of the established family of lipases/esterases, suggesting that it could be considered as a new family. The purified enzyme showed broad substrate specificity with the highest hydrolytic activity against p-nitrophenyl butyrate (C4). EstLiu showed remarkable activity (75%) at 0 °Cand the optimal activity at pH 8.0 and 30 °C with good thermostability and quickened inactivation above 60 °C. EstLiu retained 81, 103, 67 and 78% of its original activity at 50% (v/v) in ethanol, isopropanol, DMSO and ethylene glycol, respectively. In the presence of Tween 20, Tween 80 and Triton X-100, EstLiu showed 88, 100 and 117% of relative activity. It is also co-factor independent. The high activity at low temperature and desirable stability in organic solvents and salts of this novel family esterase represents a good evidence of novel biocatalyst. Overall, this novel enzyme showed better activity than previously reported esterases in extreme reaction conditions and could promote the reaction in both aqueous and non-aqueous conditions, indicating its great potential for industrial applications.     

Serum esterase activities and hyperlipidaemia in the streptozotocin -diabetic rat

The levels of activity of four serum esterases were measured in control and streptozotocin-diabetic rats for a period of 6 months. Pseudocholinesterase activity was significantly elevated in the diabetic rats at all points tested, reaching 250% of control activity at 6 months. Levels of paraoxonase activity progressively decreased with time in the diabetic rats, being 36% lower than in controls at 6 months. No significant differences in either serum arylesterase or carboxylesterase activity between control and diabetic rats were observed.     

Atomic insight into designed carbamate-based derivatives as acetylcholine esterase (AChE) inhibitors: a computational study by multiple molecular docking and molecular dynamics simulation

Over 100 variants have been designed and studied, using multiple docking methods such as Autodock Vina, ArgusLab, Molegro Virtual Docker, and Hex-Cuda, to study the effect of alteration in the structure of carbamate-based acetylcholyne esterase (AChE) inhibitors. Sixteen selected systems were then subjected to 14 ns molecular dynamics (MD) simulations. Results from all the docking methods are in agreement. Variants that involved biphenyl substituents possess the most negative binding energies in the ?37.64 to ?39.31 kJ mol^?1 range due to their π–π interactions with AChE aromatic residues. The root mean square deviation values showed that all of these components achieved equilibration after 6 ns. Gyration radius (R_g) and solvent accessibility surface area were calculated to further investigate the AChE conformational changes in the presence of these components. MD simulation results suggested that these components might interact with AChE, possibly with no major changes in AChE secondary and tertiary structures.     

Aggressiveness and Reproduction of Four Meloidogyne arenaria Populations on Soybean

Aggressiveness and reproduction differed among four geographical populations of M. arenaria on six soybean cultivars in field microplots. These differences were consistent over 3 years. The populations did not differ in virulence; i.e., population by cultivar interactions were not significant. Perineal pattern morphology, the North Carolina differential host test, chromosome counts of immature oocytes, and esterase phenotypes confirmed that the four populations were M. arenaria. Three populations were host race 2 and one population was host race 1.     

Production of acetyl esterase during wood biodegradation byCoriolus versicolor

A role of acetyl esterase in wood biodegradation byCoriolus versicolor was examined by the assay of enzyme production and the chemical analysis of decayed wood meal of Japanese beech (Fagus crenata). Enzyme assay demonstrated that the degradation proceeded in two stages and acetyl esterase production was correlated with the cellulolytic and xylanolytic enzyme production in the second stage, not with the production of phenol-oxidizing enzymes. From the results of chemical analysis, acetyl and xylose contents in wood meal were observed to decrease simultaneously in the second stage. In contrast, rapid decrease of lignin was recognized during the initial three wk of incubation, and it was closely related with the production of phenol-oxidizing enzymes in the first stage. These results show that acetyl esterase ofC. versicolor participates in the degradation of acetylxylan and acts with the cellulolytic and xylanolytic systems, not with the ligninolytic system.