Recent advances in techniques of liver resection

Molecular cloning, overexpression, characterization, and In silico modelling analysis of a novel GDSL autotransporter-dependent outer membrane lipase (OML) of Pseudomonas guariconensis

The outer membrane lipase (oml) gene, encoding a novel autotransporter-dependent lipase from Pseudomonas guariconensis, was cloned and sequenced. The oml gene has an open reading frame of 1866 bp. It encodes the 621 amino acid autotransporter-dependent GDSL lipase (OML), which has the highest sequence similarity (64.08 %) with the EstA of Pseudomonas aeruginosa (PDB:3kvn.1. A). OML was expressed and purified, which showed a purified band of approximately 70 kDa. The purified enzyme showed maximum activity at pH 9 and 40 °C. Substrate specificity studies and kinetic study by Lineweaver-Burk plot of purified OML showed Km of 1.27 mM and Vmax of 333.33 U/mL with p-nitrophenyl palmitate. The purified enzyme showed good stability in the presence of hexane, methanol, and ethanol, while the presence of the metal ion Mg2+ showed maximum lipase activity. Bioinformatics analysis supported the in vitro findings by predicting enzyme substrate specificity towards long-chain fatty acids and fatty acids with shorter chain lengths. The stability of the interaction of the protein-ligand complex (OML-ricinoleic acid) was confirmed using MDS and castor oil bioconversion using purified OML was confirmed using High-Performance Liquid Chromatography (HPLC).

Esterases as emerging biocatalysts: Mechanistic insights, genomic and metagenomic, immobilization, and biotechnological applications

Esterase enzymes are a family of hydrolases that catalyze the breakdown and formation of ester bonds. Esterases have gained a prominent position in today's world's industrial enzymes market. Due to their unique biocatalytic attributes, esterases contribute to environmentally sustainable design approaches, including biomass degradation, food and feed industry, dairy, clothing, agrochemical (herbicides, insecticides), bioremediation, biosensor development, anticancer, antitumor, gene therapy, and diagnostic purposes. Esterases can be isolated by a diverse range of mammalian tissues, animals, and microorganisms. The isolation of extremophilic esterases increases the interest of researchers in the extraction and utilization of these enzymes at the industrial level. Genomic, metagenomic, and immobilization techniques have opened innovative ways to extract esterases and utilize them for a longer time to take advantage of their beneficial activities. The current study discusses the types of esterases, metagenomic studies for exploring new esterases, and their biomedical applications in different industrial sectors.

PTCL1-EstA from Paenarthrobacter aurescens TC1, a Candidate for Industrial Application Belonging to the VIII Esterase Family

The esterase PTCL1-EstA from Paenarthrobacter aurescens TC1 was expressed in Escherichia coli and characterized. An 1152 bp open reading frame encoding a 383 amino acid polypeptide was successfully expressed, the C-terminally His6-tagged PTCL1-EstA enzyme was purified, and the predicted molecular mass of the purified PTCL1-EstA was 40.6 kDa. The EstA family serine hydrolase PTCL1-EstA belongs to the esterase family VIII, contains esterase-labeled S-C-S-K sequences, and homologous class C beta-lactamase sequences. PTCL1-EstA favored p-nitrophenyl esters with C2-C6 chain lengths, but it was also able to hydrolyze long-chain p-nitrophenyl esters. Homology modelling and substrate docking predicted that Ser59 was an active site residue in PTCL1-EstA, as well as Tyr148, Ala325, and Asp323, which are critical in catalyzing the enzymatic reaction of p-nitrophenyl esters. PTCL1-EstA reached the highest specific activity against p-nitrophenyl butyrate (C4) at pH 7.0 and 45 °C but revealed better thermal stability at 40 °C and maintained high relative enzymatic activity and stability at pH 5.0–9.0. Fermentation medium optimization for PTCL1-EstA increased the enzyme activity to 510.76 U/mL, tapping the potential of PTCL1-EstA for industrial production.

Novel phenolic antimicrobials enhanced activity of iminodiacetate prodrugs against biofilm and planktonic bacteria

Prodrugs are pharmacologically attenuated derivatives of drugs that undergo bioconversion into the active compound once reaching the targeted site, thereby maximizing their efficiency. This strategy has been implemented in pharmaceuticals to overcome obstacles related to absorption, distribution, and metabolism, as well as with intracellular dyes to ensure concentration within cells. In this study, we provide the first examples of a prodrug strategy that can be applied to simple phenolic antimicrobials to increase their potency against mature biofilms. The addition of (acetoxy)methyl iminodiacetate groups increases the otherwise modest potency of simple phenols. Biofilm-forming bacteria exhibit a heightened tolerance toward antimicrobial agents, thereby accentuating the need for new antibiotics as well as those, which incorporate novel delivery strategies to enhance activity toward biofilms.

Up-to-date intraoperative computer assisted solutions for liver surgery

Computer assisted surgical planning allowed for a better selection of patients, evaluation of operative strategy, appropriate volumetric measurements, identification of anatomical risks, definition of tumour resection margins and choice of surgical approach in liver oncologic resections and living donor liver transplantations. Although preoperative computer surgical analysis has been widely used in daily clinical practice, intraoperative computer assisted solutions for risk analysis and navigation in liver surgery are not widely available or still under clinical evaluation. Computer science technology can efficiently assist modern surgeons during complex liver operations, mainly by providing image guidance with individualized 2D images and 3D models of the various anatomical and pathological structures of interest. Intraoperative computer assisted liver surgery is particularly useful in complex parenchyma-sparing hepatectomies, for intraoperative risk analysis and for the effective treatment of colorectal metastases after neoadjuvant therapy or when they are multiple. In laparoscopic liver surgery, intraoperative computer aid is definitively more important as, apart from a restricted field of view, there is also loss of the fine haptic feedback. Intraoperative computer assisted developments face challenges that prevent their application in daily clinical practice. There is a vast variety of studies regarding intraoperative computer assisted liver surgery but there are no clear objective measurements in order to compare them and select the most effective solutions. An overview of up-to-date intraoperative computer assisted solutions for liver surgery will be discussed.

Microbial esterases and ester prodrugs: An unlikely marriage for combating antibiotic resistance

The rise of antibiotic resistance necessitates the search for new platforms for drug development. Prodrugs are common tools for overcoming drawbacks typically associated with drug formulation and delivery, with ester prodrugs providing a classic strategy for masking polar alcohol and carboxylic acid functionalities and improving cell permeability. Ester prodrugs are normally designed to have simple ester groups, as they are expected to be cleaved and reactivated by a wide spectrum of cellular esterases. However, a number of pathogenic and commensal microbial esterases have been found to possess significant substrate specificity and can play an unexpected role in drug metabolism. Ester protection can also introduce antimicrobial properties into previously nontoxic drugs through alterations in cell permeability or solubility. Finally, mutation to microbial esterases is a novel mechanism for the development of antibiotic resistance. In this review, we highlight the important pathogenic and xenobiotic functions of microbial esterases and discuss the development and application of ester prodrugs for targeting microbial infections and combating antibiotic resistance. Esterases are often overlooked as therapeutic targets. Yet, with the growing need to develop new antibiotics, a thorough understanding of the specificity and function of microbial esterases and their combined action with ester prodrug antibiotics will support the design of future therapeutics.

Autotransporter domain-dependent enzymatic analysis of a novel extremely thermostable carboxylesterase with high biodegradability towards pyrethroid pesticides

The EstPS1 gene, which encodes a novel carboxylesterase of Pseudomonas synxantha PS1 isolated from oil well-produced water, was cloned and sequenced. EstPS1 has an open reading frame of 1923 bp and encodes the 640-amino acid carboxylesterase (EstPS1), which contains an autotransporter (AT) domain (357–640 amino acids). Homology analysis revealed that EstPS1 shared the highest identity (88%) with EstA from Pseudomonas fluorescens A506 (NCBI database) and belonged to the carboxylesterase family (EC 3.1.1.1). The optimum pH and temperature of recombinant EstPS1 were found to be 8.0 and 60 °C, respectively. EstPS1 showed high thermostability, and the half-lives (T_1/2 thermal inactivation) at 60, 70, 80, 90, and 100 °C were 14 h, 2 h, 31 min, 10 min, and 1 min, respectively. To understand the role of the AT domain in carboxylesterase, AT domain-truncated carboxylesterase (EstPS1ΔAT) was generated. EstPS1ΔAT showed a clearly decreased secretion rate, owing to the AT domain strongly improved secretory expression in the heterogeneous system. EstPS1 degraded various pyrethroid pesticides, and hydrolysis efficiencies were dependent on the pyrethroid molecular structure. EstPS1 degraded all the tested pyrethroid pesticides and hydrolysed the p-nitrophenyl esters of medium-short-chain fatty acids, indicating that EstPS1 is an esterase with broad specificity.

Cell surface display of cold-active esterase EstPc with the use of a new autotransporter from Psychrobacter cryohalolentis K5(T)

We have cloned the gene coding for AT877-a new predicted member of the autotransporter protein family with an esterase passenger domain from permafrost bacterium Psychrobacter cryohalolentis K5(T). Expression of AT877 gene in Escherichia coli resulted in accumulation of the recombinant autotransporter in the outer membrane fraction and at the surface of the induced cells. AT877 displayed maximum hydrolytic activity toward medium-chain p-nitrophenyl esters (C8-C10) at 50 °C and was resistant to the presence of several metal ions, organic solvents and detergents. Previously, we have described a cold-active esterase EstPc from the same bacterium which possesses high activity at low temperatures and relatively high thermal stability. To construct a cell surface display system for EstPc, the hybrid autotransporter gene coding for EstPc with the α-helical linker and the translocator domain from AT877 was constructed and expressed in E. coli. According to the results of the cell fractionation studies and esterase activity measurements, the EstPc passenger was successfully displayed at the surface of the induced cells. It demonstrated a temperature optimum at 15-25 °C and a substrate preference toward p-nitrophenyl butyrate (C4). Obtained results provide a new example of the biotechnologically relevant enzyme from the permafrost microbial community with potential applications for the conversion of short- and medium-chain ester substrates and a basis for the construction of a new cell surface display platform.

The intracellular citrus huanglongbing bacterium, 'Candidatus Liberibacter asiaticus' encodes two novel autotransporters

Proteins secreted by the type V secretion system (T5SS), known as autotransporters, are large extracellular virulence proteins localized to the bacterial poles. In this study, we characterized two novel autotransporter proteins of 'Candidatus Liberibacter asiaticus' (Las), and redesignated them as LasAI and LasAII in lieu of the previous names HyvI and HyvII. As a phloem-limited, intracellular bacterial pathogen, Las has a significantly reduced genome and causes huanglongbing (HLB), a devastating disease of citrus worldwide. Bioinformatic analyses revealed that LasAI and LasAII share the structural features of an autotransporter family containing large repeats of a passenger domain and a unique C-terminal translocator domain. When fused to the GFP gene and expressed in E. coli, the LasAI C-terminus and the full length LasAII were localized to the bacterial poles, similar to other members of autotransporter family. Despite the absence of a typical signal peptide, LasAI was found to localize at the cell surface by immuno-dot blot using a monoclonal antibody against the partial LasAI protein. Its surface localization was also confirmed by the removal of the LasAI antigen using a proteinase K treatment of the intact bacterial cells. When co-inoculated with a P19 gene silencing suppressor and transiently expressed in tobacco leaves, the GFP-LasAI translocator targeted to the mitochondria. This is the first report that Las encodes novel autotransporters that target to mitochondria when expressed in the plants. These findings may lead to a better understanding of the pathogenesis of this intracellular bacterium.

Probing the applicability of autotransporter based surface display with the EstA autotransporter of Pseudomonas stutzeri A15

Background

Autotransporters represent a widespread family of secreted proteins in Gram-negative bacteria. Their seemingly easy secretion mechanism and modular structure make them interesting candidates for cell surface display of heterologous proteins. The most widely applied host organism for this purpose is Escherichia coli. Pseudomonas stutzeri A15 is an interesting candidate host for environmentally relevant biotechnological applications. With the recently characterized P. stutzeri A15 EstA autotransporter at hand, all tools for developing a surface display system for environmental use are available. More general, this system could serve as a case-study to test the broad applicability of autotransporter based surface display.

Results

Based on the P. stutzeri A15 EstA autotransporter β-domain, a surface display expression module was constructed for use in P. stutzeri A15. Proof of concept of this module was presented by successful surface display of the original EstA passenger domain, which retained its full esterase activity. Almost all of the tested heterologous passenger domains however were not exposed at the cell surface of P. stutzeri A15, as assessed by whole cell proteinase K treatment. Only for a beta-lactamase protein, cell surface display in P. stutzeri A15 was comparable to presentation of the original EstA passenger domain. Development of expression modules based on the full-length EstA autotransporter did not resolve these problems.

Conclusions

Since only one of the tested heterologous passenger proteins could be displayed at the cell surface of P. stutzeri A15 to a notable extent, our results indicate that the EstA autotransporter cannot be regarded as a broad spectrum cell surface display system in P. stutzeri A15.