Enhanced esterification activity through interfacial activation and cross‐linked immobilization mechanism of Rhizopus oryzae lipase in a nonaqueous medium

Interfacial activation via surfactant (Tween 80, Triton X‐100) treatment was conducted to improve the esterification activity of Rhizopus oryzae lipase that had undergone immobilization through cross‐linked enzyme aggregates (CLEA®) technique. Surfactant pretreated immobilized enzymes exhibited better esterification activity compared to free and non‐pretreated immobilized enzyme (Control CLEAs) since higher conversion rates were obtained within shorter times. The superiority of surfactant pretreated CLEAs, especially Tween 80 pretreated CLEAs (T 80 PT CLEAs), were clearly pronounced when longer alcohols were used as substrates. Conversion values exceeded 90% for octyl octanoate, oleyl octanoate and oleyl oleate synthesis with T 80 PT CLEAs whereas Control CLEAs and free enzyme showed no activity. Maximum conversions were achieved in the case equal molars of the substrates or in the case excess of the alcohol to acid in cyclohexane. In solvent free medium containing equal molars of substrates the conversion rates were 85% and 87% with T 80 PT CLEAs respectively for octyl octanoate and oleyl oleate within 2 hours. T 80 PT CLEAs showed 59% of its original activity after 7 consecutive usage for oleyl oleate synthesis. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:899–904, 2016     

Theaflavin‐3,3´‐digallate increases the antibacterial activity of β‐lactam antibiotics by inhibiting metallo‐β‐lactamase activity

Metallo‐β‐lactamases (MBLs) are some of the best known β‐lactamases produced by common Gram‐positive and Gram‐negative pathogens and are crucial factors in the rise of bacterial resistance against β‐lactam antibiotics. Although many types of β‐lactamase inhibitors have been successfully developed and used in clinical settings, no MBL inhibitors have been identified to date. Nitrocefin, checkerboard and time‐kill assays were used to examine the enzyme behaviour in vitro. Molecular docking calculation, molecular dynamics simulation, calculation of the binding free energy and ligand‐residue interaction decomposition were used for mechanistic research. The behaviour of the enzymes in vivo was investigated by a mouse infection experiment. We showed that theaflavin‐3,3´‐digallate (TFDG), a natural compound lacking antibacterial activities, can inhibit the hydrolysis of MBLs. In the checkerboard and time‐kill assays, we observed a synergistic effect of TFDG with β‐lactam antibiotics against methicillin‐resistant Staphylococcus aureus BAA1717. Molecular dynamics simulations were used to identify the mechanism of the inhibition of MBLs by TFDG, and we observed that the hydrolysis activity of the MBLs was restricted by the binding of TFDG to Gln242 and Ser369. Furthermore, the combination of TFDG with β‐lactam antibiotics showed effective protection in a mouse Staphylococcus aureus pneumonia model. These findings suggest that TFDG can effectively inhibit the hydrolysis activity of MBLs and enhance the antibacterial activity of β‐lactam antibiotics against pathogens in vitro and in vivo.     

Improved specific productivity in cephalexin synthesis by immobilized PGA in silica magnetic micro‐particles

There is a marked trend in pharmaceutical industry towards the replacement of classical organic methods by “green” alternatives that minimize or eliminate the generation of waste and avoid, where possible, the use of toxic and/or hazardous reagents and solvents. In this work the kinetically controlled synthesis of cephalexin by soluble and penicillin G acylase immobilized in sol–gel micro‐particles with magnetic properties was performed in aqueous media with PGME and 7‐ADCA as substrates, at different concentrations of substrate, temperature, pH, enzyme to substrate ratio and acyl donor to nucleophile ratio. Excess acyl donor had a strong effect on cephalexin productivity. A PGME/7‐ADCA ratio of 3 was considered optimum. A maximum specific productivity of at 160 mM 7‐ADCA, 480 mM PGME and low enzyme to substrate ratio at 32.5 U mmol^?1 7‐ADCA was obtained with immobilized PGA in full aqueous medium, suggesting that diffusional limitations were minimized when compared with other commercial biocatalysts. A half‐life of 133 h for the immobilized biocatalyst was estimated during cephalexin synthesis in the presence of 100 mM 7‐ADCA and 300 mM PGME, in 50 mM Tris/HCl at pH 7.2 and 14°C. These results compare quite favorably with those previously reported for the kinetically controlled synthesis of cephalexin. Biotechnol. Bioeng. 2010;107: 753–762. © 2010 Wiley Periodicals, Inc.     

Novel Magnetic Cross‐Linked Lipase Aggregates for Improving the Resolution of (R,S)‐2‐octanol

Novel magnetic cross‐linked lipase aggregates were fabricated by immobilizing the cross‐linked lipase aggregates onto magnetic particles with a high number of ‐NH₂ terminal groups using p‐benzoquinone as the cross‐linking agent. At the optimal fabrication conditions, 100% of immobilization efficiency and 139% of activity recovery of the magnetic cross‐linked lipase aggregates were achieved. The magnetic cross‐linked lipase aggregates were able to efficiently resolve (R, S)‐2‐octanol, and retained 100% activity and 100% enantioselectivity after 10 cycles of reuse, whereas the cross‐linked lipase aggregates only retained about 50% activity and 70% enantioselectivity due to insufficient cross‐linking. These results provide a great potential for industrial applications of the magnetic cross‐linked lipase aggregates. Chirality 27:199–204, 2015. © 2014 Wiley Periodicals, Inc.     

Modification of Immobead 150 support for protein immobilization: Effects on the properties of immobilized Aspergillus oryzae β‐galactosidase

We studied the modification of Immobead 150 support by either introducing aldehyde groups using glutaraldehyde (Immobead‐Glu) or carboxyl groups through acid solution (Immobead‐Ac) for enzyme immobilization by covalent attachment or ion exchange, respectively. These two types of immobilization were compared with the use of epoxy groups that are now provided on a commercial support. We used Aspergillus oryzae β‐galactosidase (Gal) as a model protein, immobilizing it on unmodified (epoxy groups, Immobead‐Epx) and modified supports. Immobilization yield and efficiency were tested as a function of protein loading (10–500 mg g^?1 support). Gal was efficiently immobilized on the Immobeads with an immobilization efficiency higher than 75% for almost all supports and protein loads. Immobilization yields significantly decreased when protein loadings were higher than 100 mg g^?1 support. Gal immobilized on Immobead‐Glu and Immobead‐Ac retained approximately 60% of its initial activity after 90 days of storage at 4°C. The three immobilized Gal derivatives presented higher half‐lifes than the soluble enzyme, where the half‐lifes were twice higher than the free Gal at 73°C. All the preparations were moderately operationally stable when tested in lactose solution, whey permeate, cheese whey, and skim milk, and retained approximately 50% of their initial activity after 20 cycles of hydrolyzing lactose solution. The modification of the support with glutaraldehyde provided the most stable derivative during cycling in cheese whey hydrolysis. Our results suggest that the Immobead 150 is a promising support for Gal immobilization. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:934–943, 2018     

Mapping of O‐linked β‐N‐acetylglucosamine modification sites in key contractile proteins of rat skeletal muscle

O‐linked β‐N‐acetylglucosamine (O‐GlcNAc) is a widespread modification of serine/threonine residues of nucleocytoplasmic proteins. Recently, several key contractile proteins in rat skeletal muscle (i.e., myosin heavy and light chains and actin) were identified as O‐GlcNAc modified. Moreover, it was demonstrated that O‐GlcNAc moieties involved in contractile protein interactions could modulate Ca²⁺ activation parameters of contraction. In order to better understand how O‐GlcNAc can modulate the contractile activity of muscle fibers, we decided to identify the sites of O‐GlcNAc modification in purified contractile protein homogenates. Using an MS‐based method that relies on mild β‐elimination followed by Michael addition of DTT (BEMAD), we determined the localization of one O‐GlcNAc site in the subdomain four of actin and four O‐GlcNAc sites in the light meromyosin region of myosin heavy chains (MHC). According to previous reports concerning the role of these regions, our data suggest that O‐GlcNAc sites might modulate the actin–tropomyosin interaction, and be involved in MHC polymerization or interactions between MHC and other contractile proteins. Thus, the results suggest that this PTM might be involved in protein–protein interactions but could also modulate the contractile properties of skeletal muscle.     

The stress response neuropeptide CRF increases amyloid‐β production by regulating γ‐secretase activity

The biological underpinnings linking stress to Alzheimer's disease (AD) risk are poorly understood. We investigated how corticotrophin releasing factor (CRF), a critical stress response mediator, influences amyloid‐β (Aβ) production. In cells, CRF treatment increases Aβ production and triggers CRF receptor 1 (CRFR1) and γ‐secretase internalization. Co‐immunoprecipitation studies establish that γ‐secretase associates with CRFR1; this is mediated by β‐arrestin binding motifs. Additionally, CRFR1 and γ‐secretase co‐localize in lipid raft fractions, with increased γ‐secretase accumulation upon CRF treatment. CRF treatment also increases γ‐secretase activity in vitro, revealing a second, receptor‐independent mechanism of action. CRF is the first endogenous neuropeptide that can be shown to directly modulate γ‐secretase activity. Unexpectedly, CRFR1 antagonists also increased Aβ. These data collectively link CRF to increased Aβ through γ‐secretase and provide mechanistic insight into how stress may increase AD risk. They also suggest that direct targeting of CRF might be necessary to effectively modulate this pathway for therapeutic benefit in AD, as CRFR1 antagonists increase Aβ and in some cases preferentially increase Aβ42 via complex effects on γ‐secretase.     

The role of calcium in apoptosis induced by 7β‐hydroxycholesterol and cholesterol‐5β,6β‐epoxide

Oxysterols, such as 7β‐hydroxy‐cholesterol (7β‐OH) and cholesterol‐5β,6β‐epoxide (β‐epoxide), may have a central role in promoting atherogenesis. This is thought to be predominantly due to their ability to induce apoptosis in cells of the vascular wall and in monocytes/macrophages. Although there has been extensive research regarding the mechanisms through which oxysterols induce apoptosis, much remains to be clarified. Given that experimental evidence has long associated alterations of calcium (Ca²⁺) homeostasis to apoptotic cell death, the aim of the present study was to determine the influence of intracellular Ca²⁺ changes on apoptosis induced by 7β‐OH and β‐epoxide. Ca²⁺ responses in differentiated U937 cells were assessed by epifluorescence video microscopy, using the ratiometric dye fura‐2. Over 15‐min exposure of differentiated U937 cells to 30 μM of 7β‐OH induced a slow but significant rise in fura‐2 ratio. The Ca²⁺ channel blocker nifedipine and the chelating agent EGTA blocked the increase in cytoplasmic Ca²⁺. Moreover, dihydropyridine (DHP) binding sites identified with BODIPY‐FLX‐DHP were blocked following pretreatment with nifedipine, indicating that the influx of Ca²⁺ occurred through L‐type channels. However, following long‐term incubation with 7β‐OH, elevated levels of cytoplasmic Ca²⁺ were not maintained and nifedipine did not provide protection against apoptotic cell death. Our results indicate that the increase in Ca²⁺ may be an initial trigger of 7β‐OH–induced apoptosis, but following chronic exposure to the oxysterol, the influence of Ca²⁺ on apoptotic cell death appears to be less significant. In contrast, Ca²⁺ did not appear to be involved in β‐epoxide–induced apoptosis. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:324–332, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20295     

Examination of the active secondary structure of the peptide 101.10, an allosteric modulator of the interleukin‐1 receptor,by positional scanning using β‐amino γ‐lactams

The relationship between the conformation and biological activity of the peptide allosteric modulator of the interleukin‐1 receptor 101.10 (D ‐Arg‐D ‐Tyr‐D ‐Thr‐D ‐Val‐D ‐Glu‐D ‐Leu‐D ‐Ala‐NH₂) has been studied using (R)‐ and (S)‐Bgl residues. Twelve Bgl peptides were synthesized using (R)‐ and (S)‐cyclic sulfamidate reagents derived from L ‐ and D ‐aspartic acid in an optimized Fmoc‐compatible protocol for efficient lactam installment onto the supported peptide resin. Examination of these (R)‐ and (S)‐Bgl 101.10 analogs for their potential to inhibit IL‐1β‐induced thymocyte cell proliferation using a novel fluorescence assay revealed that certain analogs exhibited retained and improved potency relative to the parent peptide 101.10. In light of previous reports that Bgl residues may stabilize type II′β‐turn‐like conformations in peptides, CD spectroscopy was performed on selected compounds to identify secondary structure necessary for peptide biological activity. Results indicate that the presence of a fold about the central residues of the parent peptide may be important for activity. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Characterization of an Importin α/β‐recognized nuclear localization signal in β‐dystroglycan

β‐dystroglycan (β‐DG) is a widely expressed transmembrane protein that plays important roles in connecting the extracellular matrix to the cytoskeleton, and thereby contributing to plasma membrane integrity and signal transduction. We previously observed nuclear localization of β‐DG in cultured cell lines, implying the existence of a nuclear targeting mechanism that directs it to the nucleus instead of the plasma membrane. In this study, we delineate the nuclear import pathway of β‐DG, characterizing a functional nuclear localization signal (NLS) in the β‐DG cytoplasmic domain, within amino acids 776–782. The NLS either alone or in the context of the whole β‐DG protein was able to target the heterologous GFP protein to the nucleus, with site‐directed mutagenesis indicating that amino acids R⁷⁷⁹ and K⁷⁸⁰ are critical for NLS functionality. The nuclear transport molecules Importin (Imp)α and Impβ bound with high affinity to the NLS of β‐DG and were found to be essential for NLS‐dependent nuclear import in an in vitro reconstituted nuclear transport assay; cotransfection experiments confirmed the dependence on Ran for nuclear accumulation. Intriguingly, experiments suggested that tyrosine phosphorylation of β‐DG may result in cytoplasmic retention, with Y⁸⁹² playing a key role. β‐DG thus follows a conventional Impα/β‐dependent nuclear import pathway, with important implications for its potential function in the nucleus. J. Cell. Biochem. 110: 706–717, 2010. © 2010 Wiley‐Liss, Inc.     

Cytotoxic (9βH)‐Pimarane and (9βH)‐17‐Norpimarane Diterpenes from the Tuber of Icacina trichantha

Three (9βH)‐pimaranes, 1, 2 , and 3 , and two (9βH)‐17‐norpimaranes, 4 and 5 , belonging to a rare compound class in nature, were obtained from the tubers of Icacina trichantha for the first time. Compound 1 is a new natural product, and 2 – 5 have been previously reported. The structures were elucidated based on NMR and MS data, and optical rotation values. The absolute configurations of (9βH)‐pimaranes were unambiguously established based on X‐ray crystallographic analysis. Full NMR signal assignments for the known compounds 2, 4 , and 5 , which were not available in previous publications, are also reported. All five isolates displayed cytotoxic activities on MDA‐MB‐435 cells (IC₅₀ 0.66–6.44 μM ), while 2, 3 , and 4 also exhibited cytotoxicities on HT‐29 cells (IC₅₀ 3.00–4.94 μM ).     

Blockade of JAK2 activity suppressed accumulation of β‐catenin in leukemic cells

The Wnt/β‐catenin pathway has been implicated in leukemogenesis. We found β‐catenin abnormally accumulated in both human acute T cell leukemia Jurkat cells and human erythroleukemia HEL cells. β‐Catenin can be significantly down‐regulated by the Janus kinase 2 specific inhibitor AG490 in these two cells. AG490 also reduces the luciferase activity of a reporter plasmid driven by LEF/β‐catenin promoter. Similar results were observed in HEL cells infected with lentivirus containing shRNA against JAK2 gene. After treatment with 50 µM AG490 or shRNA, the mRNA expression levels of β‐catenin, APC, Axin, β‐Trcp, GSK3α, and GSK3β were up‐regulated within 12–16 h. However, only the protein levels of GSK3β and β‐Trcp were found to have increased relative to untreated cells. Knockdown experiments revealed that the AG490‐induced inhibition of β‐catenin can be attenuated by shRNA targeting β‐TrCP. Taken together; these results suggest that β‐Trcp plays a key role in the cross‐talk between JAK/STAT and Wnt/β‐catenin signaling in leukemia cells. J. Cell. Biochem. 111: 402–411, 2010. © 2010 Wiley‐Liss, Inc.     

Evaluation of the double‐disk synergy test for New Delhi metallo‐β‐lactamase‐1 and other metallo‐β‐lactamase producing gram‐negative bacteria by using metal‐ethylenediaminetetraacetic acid complexes

New Delhi metallo‐β‐lactamase‐1 (NDM‐1), one of the metallo‐β‐lactamases (MBLs), has been identified from clinical isolates worldwide. Rapid detection of NDM‐1 producers is necessary to prevent their dissemination. Seven types of EDTA complexes were evaluated as MBL inhibitors in double‐disk synergy tests (DDSTs), resulting in detection of the first isolate of NDM‐1‐producing Escherichia coli (NDM‐1 Dok01) in Japan. NDM‐1 Dok01 was detected when EDTA magnesium disodium salt tetrahydrate (Mg‐EDTA), EDTA calcium disodium salt dihydrate, EDTA cobalt disodium salt tetrahydrate and EDTA copper disodium salt tetrahydrate were used as MBL inhibitors. The sensitivity and specificity of DDSTs using Mg‐EDTA for 75 MBL producers and 25 non‐MBL producers were 96.0% and 100%, respectively. These findings indicate that the DDST method using Mg‐EDTA can detect MBL‐producing strains, including NDM‐1 producers.     

One ring to rule them all: Current trends in combating bacterial resistance to the β‐lactams

From humble beginnings of a contaminated petri dish, β‐lactam antibiotics have distinguished themselves among some of the most powerful drugs in human history. The devastating effects of antibiotic resistance have nevertheless led to an “arms race” with disquieting prospects. The emergence of multidrug resistant bacteria threatens an ever‐dwindling antibiotic arsenal, calling for new discovery, rediscovery, and innovation in β‐lactam research. Here the current state of β‐lactam antibiotics from a structural perspective was reviewed.