A cold-active esterase with a substrate preference for vinyl esters from a psychrotroph, Acinetobacter sp. strain no. 6: gene cloning, purification, and characterization

Together Is Better: The Rumen Microbial Community as Biological Toolbox for Degradation of Synthetic Polyesters

Identfication of plastics degradation and microbial community analysis of Rumen.

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Exogenous gibberellin weakens lipid breakdown by increasing soluble sugars levels in early germination of zanthoxylum seeds

Zanthoxylum is a precious medicinal woody plant with a very low seed germination rate in China. The gibberellin (GA) treatment extremely increased the germination rate of zanthoxylum seeds. Our previous transcriptome data showed that exogenous GA played a negative role in the expression levels of genes involved in lipid metabolism during imbibition. Our present data indicated that compared with the GA-treated seeds, the soluble sugars were more quickly consumed and lipid breakdown was prematurely and actively initiated in the water-treated seeds during the early germination. However, the application of sucrose could improve the germination of water-treated seeds and significantly inhibit lipid breakdown. Both the application of sucrose and exogenous GA could significantly reduce the catalytic activities of sugar-dependent 1 (SDP1) and isocitratelyase (ICL), the expressions of SDP1 and ICL genes, and decrease the products of lipid breakdown as well during the early germination. We suggested that exogenous GA might enhance starch hydrolysis by promoting the catalytic activity of ɑ-amylase to supplement metabolically consumed soluble sugars, thus the increased sugars levels would help to inhibit the lipid breakdown to mitigate oxidative damages in the early germination of zanthoxylum seeds. In the end, we summarized the possible molecular mechanism on the exogenous GA weakening lipid breakdown by increasing soluble sugars levels in the early germination of zanthoxylum seeds.

Isolation of a fluoroglycofen-degrading KS-1 strain and cloning of a novel esterase gene fluE

The bacterium KS-1, capable of degrading fluoroglycofen, was isolated from sludge collected at a herbicide factory. The isolate was identified as Lysinibacillus sp. according to its phenotypic features and 16S rDNA phylogeny. KS-1 degraded 85.25% of the fluoroglycofen (50 mg L-1) within 3 days of incubation. The optimum temperature and pH for fluoroglycofen degradation were 30°C and 7.0, respectively. Furthermore, Zn2+ and Cu2+ could significantly decrease the degradation rate. Three degradation products, which appeared during KS-1-mediated fluoroglycofen metabolism, were identified as deethyl-fluoroglycofen, acifluorfen and decarboxylate-acifluorfen. The fluE gene, which encodes a novel esterase that catalyzes the cleavage of carboxyl ester bonds of fluoroglycofen, was cloned from the KS-1 strain. Sequence alignment reveals that FluE shares 30%-40% amino acid sequence identity with members of the hormone sensitive lipase family. FluE was expressed in Escherichia coli BL21 and purified by Ni-NTA affinity chromatography. Purified FluE could efficiently hydrolyze fluoroglycofen and short-chain p-nitrophenol esters. However, no lipolytic activity was observed with esters containing acyl chains longer than 10 carbon atoms, thereby indicating that this enzyme is an esterase.

Structure and activity of the cold-active and anion-activated carboxyl esterase OLEI01171 from the oil-degrading marine bacterium Oleispira antarctica

The uncharacterized α/β-hydrolase protein OLEI01171 from the psychrophilic marine bacterium Oleispira antarctica belongs to the PF00756 family of putative esterases, which also includes human esterase D. In the present paper we show that purified recombinant OLEI01171 exhibits high esterase activity against the model esterase substrate α-naphthyl acetate at 5-30°C with maximal activity at 15-20°C. The esterase activity of OLEI01171 was stimulated 3-8-fold by the addition of chloride or several other anions (0.1-1.0 M). Compared with mesophilic PF00756 esterases, OLEI01171 exhibited a lower overall protein thermostability. Two crystal structures of OLEI01171 were solved at 1.75 and 2.1 Å resolution and revealed a classical serine hydrolase catalytic triad and the presence of a chloride or bromide ion bound in the active site close to the catalytic Ser148. Both anions were found to co-ordinate a potential catalytic water molecule located in the vicinity of the catalytic triad His257. The results of the present study suggest that the bound anion perhaps contributes to the polarization of the catalytic water molecule and increases the rate of the hydrolysis of an acyl-enzyme intermediate. Alanine replacement mutagenesis of OLEI01171 identified ten amino acid residues important for esterase activity. The replacement of Asn225 by lysine had no significant effect on the activity or thermostability of OLEI01171, but resulted in a detectable increase of activity at 35-45°C. The present study has provided insight into the molecular mechanisms of activity of a cold-active and anion-activated carboxyl esterase.

A novel cold-adapted esterase from Salinisphaera sp. P7-4: gene cloning, overproduction, and characterization

Salinisphaera sp. P7-4 was isolated from the intestine of silver whiting, Sillago japonicas caught in the Pacific Ocean, and the esterase gene was cloned using the shotgun method. The amino acid sequence deduced from the nucleotide sequence (951 bp) corresponded to a protein of 316 amino acid residues with a molecular weight of 34,443. The esterase had 46 and 44% identities with the esterase enzymes of Ralstonia eutropha JMP134 and Rhodopseudomonas palustris HaA2, respectively. The primary structure of P7-4 esterase showed the conserved catalytic triad (Ser, Asp, His), consensus pentapeptide GXSXG, and oxyanion hole sequence (HG). The protein P7-4 was successfully expressed in Escherichia coli in a biologically active form. The enzyme showed high catalytic activity at low temperatures (5-25° C) with an activation energy of 2.18 kcal/mol. This result indicated that the esterase from Salinisphaera sp. P7-4 is a new cold-adapted enzyme. The enzyme preferentially hydrolyzed acyl-group chains with short chain lengths of ≤10 carbon. Metal ions such as Cd2(+), Co2(+), Cu2(+), Hg2(+), Ni2(+) and Zn2(+) inhibited enzymatic activity. Additionally, EDTA has no effect on its activity, whereas inhibition was observed with PMSF, a serine hydrolase inhibitor.

A cold-adapted esterase from psychrotrophic Pseudoalteromas sp. strain 643A

A psychrotrophic bacterium producing a cold-adapted esterase upon growth at low temperatures was isolated from the alimentary tract of Antarctic krill Euphasia superba Dana, and classified as Pseudoalteromonas sp. strain 643A. A genomic DNA library of strain 643A was introduced into Escherichia coli TOP10F', and screening on tributyrin-containing agar plates led to the isolation of esterase gene. The esterase gene (estA, 621 bp) encoded a protein (EstA) of 207 amino acid residues with molecular mass of 23,036 Da. Analysis of the amino acid sequence of EstA suggests that it is a member of the GDSL-lipolytic enzymes family. The purification and characterization of native EstA esterase were performed. The enzyme displayed 20-50% of maximum activity at 0-20 degrees C. The optimal temperature for EstA was 35 degrees C. EstA was stable between pH 9 and 11.5. The enzyme showed activity for esters of short- to medium-chain (C(4) and C(10)) fatty acids, and exhibited no activity for long-chain fatty acid esters like that of palmitate and stearate. EstA was strongly inhibited by phenylmethylsulfonyl fluoride, 2-mercaptoethanol, dithiothreitol and glutathione. Addition of selected divalent ions e.g. Mg(2+), Co(2+) and Cu(2+) led to the reduction of enzymatic activity and the enzyme was slightly activated ( approximately 30%) by Ca(2+) ions.

A novel esterase from Ralstonia sp. M1: gene cloning, sequencing, high-level expression and characterization

A newly isolated gene from Ralstonia sp. M1, encoding an esterase, was cloned in Escherichia coli and its nucleotide sequence determined. The 1.6kb insert revealed one complete open reading frame, predicted to encode an esterase (320 aa, 34.1kDa) with a pI of 9.86. EstR contained a putative oxyanion hole H36G37, a conserved pentapeptide G103HSLG107 and a conserved catalytic His265 and Asp237. The EstR sequence shared 64-70 and 44-48% identity with the hydrolases/acyltransferases from Burkholderia strains and from Ralstonia strains, respectively, 44 and 38% identity with the lactone-specific esterase from Pseudomonas fluorescens and Mesorhizobium loti, respectively. The esterase EstR was expressed with a high level of 41mg/g wet cells. The Ni-NTA-purified esterase EstR showed an optimal activity in the temperature range 60-65 degrees C and pH range 7.5-9.0 towards p-nitrophenyl caproate. The enzyme was found to be highly resistant to many organic solvents especially induced by ethanolamine. Metal ions showed slight effect on esterase activity. The inhibitor phenylmethanesulfonyl fluoride inhibited strongly the esterase. Triton X-45 induced the activation of EstR, but other detergents slightly to strongly decreased or completely inhibited. Among tested p-NP esters, caproate was the most preferential substrate of this esterase.

Cold-active esterase from Psychrobacter sp. Ant300: gene cloning, characterization, and the effects of Gly→Pro substitution near the active site on its catalytic activity and stability

The gene encoding an esterase (PsyEst) of Psychrobacter sp. Ant300, a psychrophilic bacterium isolated from Antarctic soil, was cloned, sequenced, and expressed in Escherichia coli. PsyEst, which is a member of hormone-sensitive lipase (HSL) group of the lipase/esterase family, is a cold-active, themolabile enzyme with high catalytic activity at low temperatures (5-25 degrees C), low activation energy (e.g., 4.6 kcal/mol for hydrolysis of p-nitrophenyl butyrate), and a t(1/2) value of 16 min for thermal inactivation during incubation at 40 degrees C and pH 7.9. A three-dimensional structural model of PsyEst predicted that Gly(244) was located in the loop near the active site of PsyEst and that substitution of this amino-acid residue by proline should potentially rigidify the active-site environment of the enzyme. Thus, we introduced the Gly(244)-->Pro substitution into the enzyme. Stability studies showed that the t(1/2) value for thermal inactivation of the mutant during incubation at 40 degrees C and pH 7.9 was 11.6 h, which was significantly greater than that of the wild-type enzyme. The k(cat)/K(m) value of the mutant was lower for all substrates examined than the value of the wild type. Moreover, this amino-acid substitution caused a shift of the acyl-chain length specificity of the enzyme toward higher preference for short-chain fatty acid esters. All of these observations could be explained in terms of a decrease in active-site flexibility brought about by the mutation and were consistent with the hypothesis that cold activity and thermolability arise from local flexibility around the active site of the enzyme.

Cloning, heterologous expression, renaturation, and characterization of a cold-adapted esterase with unique primary structure from a psychrotroph Pseudomonas sp. strain B11-1

A gene coding for an esterase (PsEst1, 1911bp in length) of the psychrotrophic bacterium Pseudomonas sp. B11-1 isolated from Alaskan soil was cloned and sequenced. The deduced amino acid sequence revealed a protein of 637 amino acid residues with a molecular mass of 69 kDa. Although the expression product, PsEst1, showed no appreciable sequence similarity (less than 15% identity) to any known proteins with the established biochemical functions, it is expected to be related to the alpha/beta hydrolase superfamily because it shared sequence motifs that have been identified with this superfamily. For example, a unique 'nucleophilic elbow' motif, -Gly(36)-Asp-Ser-Leu-Asn(40)-, was identified, and Ser(38) was predicted to constitute a catalytic triad with Asp(162) and His(303). PsEst1 was overexpressed using a T7 RNA polymerase transcription (pET21a) system in the Escherichia coli BL21(DE3) cells as an inclusion body. A soluble denatured form of the enzyme was purified to homogeneity in the presence of 8M urea, and the catalytically active form of the enzyme could be obtained by subsequent removal of urea by dialysis, where the addition of 0.1% Triton X-100 was essential for the efficient renaturation of the enzyme. To our knowledge, this was the first example of the successful renaturation of the recombinant cold-adapted enzyme. The enzyme efficiently hydrolyzed vinyl and aryl esters with the C4-C6 acyl chain. The activation energy of the enzymatic p-nitrophenyl butyrate hydrolysis (20.1 kcal/mol at 10 degrees C) was significantly lower than the value (79.9 kcal/mol) of the mesophilic lipase. It was observed that the K(m) values for p-nitrophenyl butyrate in the growth temperature range of strain B11-1 (5-15 degrees C) were lower than those at higher temperatures.