Laccase-catalyzed polymerization of tyrosine-containing peptides

Improving the Microstructural and Rheological Properties of Frozen Unfermented Wheat Dough with Laccase and Ferulic Acid

The quality deterioration that is induced by freezing treatment limits the development of frozen dough technology for standardized and delayed baking. In this study, laccase (LAC) and ferulic acid (FA) were employed to improve the rheological properties and microstructure of frozen unfermented dough. The results showed that the dough with LAC + FA had a lower softening degree than the dough with FA alone. Correspondingly, LAC + FA incorporation enhanced the viscoelastic behavior of frozen unfermented dough with better stability. Furthermore, a more uniform and homogeneous gluten network was observed in the LAC + FA-supplemented dough after 21 d of storage. The structural stability of the frozen gluten sample increased after LAC + FA treatment, possibly owing to an increase in the oxidation degree of FA. Moreover, LAC + FA treatment promoted the oxidation of the sulfhydryl groups to some extent, resulting in more extensive cross-linking. LAC + FA treatment hindered the protein conformational changes typically induced by frozen storage compared with LAC alone. Overall, LAC + FA treatment has a synergistic effect on enhancing the viscoelastic behaviors of frozen unfermented dough and inhibiting the conformational variation in frozen gluten; thus, it shows promise for improving frozen dough.

Carbon-Centered Radicals in Protein Manipulation

Methods to directly post-translationally modify proteins are perhaps the most straightforward and operationally simple ways to create and study protein post-translational modifications (PTMs). However, precisely altering or constructing the C-C scaffolds pervasive throughout biology is difficult with common two-electron chemical approaches. Recently, there has been a surge of new methods that have utilized single electron/radical chemistry applied to site-specifically "edit" proteins that have started to create this potential-one that in principle could be near free-ranging. This review provides an overview of current methods that install such "edits", including those that generate function and/or PTMs, through radical C-C bond formation (as well as C-X bond formation via C• where illustrative). These exploit selectivity for either native residues, or preinstalled noncanonical protein side-chains with superior radical generating or accepting abilities. Particular focus will be on the radical generation approach (on-protein or off-protein, use of light and photocatalysts), judging the compatibility of conditions with proteins and cells, and novel chemical biology applications afforded by these methods. While there are still many technical hurdles, radical C-C bond formation on proteins is a promising and rapidly growing area in chemical biology with long-term potential for biological editing.

Cross-linking reactions in food proteins and proteomic approaches for their detection

Various protein cross-linking reactions leading to molecular polymerization and covalent aggregates have been described in processed foods. They are an undesired side effect of processes designed to reduce bacterial load, extend shelf life, and modify technological properties, as well as being an expected result of treatments designed to modify raw material texture and function. Although the formation of these products is known to affect the sensory and technological properties of foods, the corresponding cross-linking reactions and resulting protein polymers have not yet undergone detailed molecular characterization. This is essential for describing how their generation can be related to food processing conditions and quality parameters. Due to the complex structure of cross-linked species, bottom-up proteomic procedures developed to characterize various amino acid modifications associated with food processing conditions currently offer a limited molecular description of bridged peptide structures. Recent progress in cross-linking mass spectrometry for the topological characterization of protein complexes has facilitated the development of various proteomic methods and bioinformatic tools for unveiling bridged species, which can now also be used for the detailed molecular characterization of polymeric cross-linked products in processed foods. We here examine their benefits and limitations in terms of evaluating cross-linked food proteins and propose future scenarios for application in foodomics. They offer potential for understanding the protein cross-linking formation mechanisms in processed foods, and how the inherent beneficial properties of treated foodstuffs can be preserved or enhanced.

Putting precision and elegance in enzyme immobilisation with bio-orthogonal chemistry

The covalent immobilisation of enzymes generally involves the use of highly reactive crosslinkers, such as glutaraldehyde, to couple enzyme molecules to each other or to carriers through, for example, the free amino groups of lysine residues, on the enzyme surface. Unfortunately, such methods suffer from a lack of precision. Random formation of covalent linkages with reactive functional groups in the enzyme leads to disruption of the three dimensional structure and accompanying activity losses. This review focuses on recent advances in the use of bio-orthogonal chemistry in conjunction with rec-DNA to affect highly precise immobilisation of enzymes. In this way, cost-effective combination of production, purification and immobilisation of an enzyme is achieved, in a single unit operation with a high degree of precision. Various bio-orthogonal techniques for putting this precision and elegance into enzyme immobilisation are elaborated. These include, for example, fusing (grafting) peptide or protein tags to the target enzyme that enable its immobilisation in cell lysate or incorporating non-standard amino acids that enable the application of bio-orthogonal chemistry.

Evolutionary genomic relationships and coupling in MK-STYX and STYX pseudophosphatases

The dual specificity phosphatase (DUSP) family has catalytically inactive members, called pseudophosphatases. They have mutations in their catalytic motifs that render them enzymatically inactive. This study analyzes the significance of two pseudophosphatases, MK-STYX [MAPK (mitogen-activated protein kinase phosphoserine/threonine/tyrosine-binding protein]) and STYX (serine/threonine/tyrosine-interacting protein), throughout their evolution and provides measurements and comparison of their evolutionary conservation. Phylogenetic trees were constructed to show any deviation from various species evolutionary paths. Data was collected on a large set of proteins that have either one of the two domains of MK-STYX, the DUSP domain or the cdc-25 homology (CH2) /rhodanese-like domain. The distance between species pairs for MK-STYX or STYX and Ka/Ks ratio were calculated. In addition, both pseudophosphatases were ranked among a large set of related proteins, including the active homologs of MK-STYX, MKP (MAPK phosphatase)-1 and MKP-3. MK-STYX had one of the highest species-species protein distances and was under weaker purifying selection pressure than most proteins with its domains. In contrast, the protein distances of STYX were lower than 82% of the DUSP-containing proteins and was under one of the strongest purifying selection pressures. However, there was similar selection pressure on the N-terminal sequences of MK-STYX, STYX, MKP-1, and MKP-3. We next perform statistical coupling analysis, a process that reveals interconnected regions within the proteins. We find that while MKP-1,-3, and STYX all have 2 functional units (sectors), MK-STYX only has one, and that MK-STYX is similar to MKP-3 in the evolutionary coupling of the active site and KIM domain. Within those two domains, the mean coupling is also most similar for MK-STYX and MKP-3. This study reveals striking distinctions between the evolutionary patterns of MK-STYX and STYX, suggesting a very specific role for each pseudophosphatase, further highlighting the relevance of these atypical members of DUSP as signaling regulators. Therefore, our study provides computational evidence and evolutionary reasons to further explore the properties of pseudophosphatases, in particular MK-STYX and STYX.

Synergistic effects of laccase and pectin on the color changes and functional properties of meat analogs containing beet red pigment

The widening gap between current supply of meat and its future demand has increased the need to produce plant-based meat analogs. Despite ongoing technical developments, one of the unresolved challenges of plant-based meat analogs is to safely and effectively imitate the appearance of raw and cooked animal-based meat, especially the color. This study aimed to develop a more effective and safe browning system for beet red (BR) in plant-based meat analog patties using laccase (LC) and sugar beet pectin (SBP). First, we investigated the synergistic effects of SBP and LC on BR decolorization of meat analog patties. We discovered that the red tones of LC-treated patties containing BR and SBP were remarkably browned after grilling, compared to patties that did not contain SBP. Notably, this color change by LC + SBP was similar to that of beef patties. Additionally, the hardness of LC-treated meat analog patties containing BR was higher than those that did not contain BR. Interestingly, the presence of SBP and LC enhanced the browning reaction and functional properties of meat analogs containing BR. This is the first report on a browning system for meat analogs containing BR using enzymatic methods to the best of our knowledge.

Plant Copper Metalloenzymes As Prospects for New Metabolism Involving Aromatic Compounds

Copper is an important transition metal cofactor in plant metabolism, which enables diverse biocatalysis in aerobic environments. Multiple classes of plant metalloenzymes evolved and underwent genetic expansions during the evolution of terrestrial plants and, to date, several representatives of these copper enzyme classes have characterized mechanisms. In this review, we give an updated overview of chemistry, structure, mechanism, function and phylogenetic distribution of plant copper metalloenzymes with an emphasis on biosynthesis of aromatic compounds such as phenylpropanoids (lignin, lignan, flavonoids) and cyclic peptides with macrocyclizations via aromatic amino acids. We also review a recent addition to plant copper enzymology in a copper-dependent peptide cyclase called the BURP domain. Given growing plant genetic resources, a large pool of copper biocatalysts remains to be characterized from plants as plant genomes contain on average more than 70 copper enzyme genes. A major challenge in characterization of copper biocatalysts from plant genomes is the identification of endogenous substrates and catalyzed reactions. We highlight some recent and future trends in filling these knowledge gaps in plant metabolism and the potential for genomic discovery of copper-based enzymology from plants.

Laccase cross-linking of sonicated α-Lactalbumin improves physical and oxidative stability of CLA oil in water emulsion

α-lactalbumin was modified by ultrasound (US, 20 kHz, 43 ± 3.4 W/cm^-2) pre-treatments (0, 15, 30 and 60 min) and laccase cross-linking of sonicated α-lactalbumin was used to evaluate the physical and oxidative stability of conjugated linoleic acid (CLA) emulsions. The emulsions prepared with laccase cross-linking US-α-lactalbumin (α-lactalbumin treated with US pre-treatment) and US-α-lactalbumin were scrutinized for oxidative and physical stability at room temperature for two weeks of storage. Laccase cross-linking US-α-lactalbumin (Lac-US-α-lactalbumin) revealed improved physical stability in comparison with US-α-lactalbumin, specified by droplet size, structural morphology, adsorbed protein, emulsifying properties and creaming index. SDS-PAGE analysis showed that there was formation of polymers in Lac-US-α-lactalbumin emulsion. Surface hydrophobicity of Lac-US-α-lactalbumin was higher than that of US-α-lactalbumin, and gradually enhanced with the increase of ultrasound time. More importantly, the measurements of peroxide values and conjugated dienes were used to study the oxidative stability of the CLA emulsions. The Lac-US-α-lactalbumin emulsion proved to be reducing the synthesis of fatty acid hydroperoxides and less conjugated dienes compared to the native and US-α-lactalbumin emulsions. This study revealed that the combination of US pre-treatment and laccase cross-linking might be an effective technique for the modification of CLA emulsions.

Mechanisms of Manganese(II) Oxidation by Filamentous Ascomycete Fungi Vary With Species and Time as a Function of Secretome Composition

Manganese (Mn) oxides are among the strongest oxidants and sorbents in the environment, and Mn(II) oxidation to Mn(III/IV) (hydr)oxides includes both abiotic and microbially-mediated processes. While white-rot Basidiomycete fungi oxidize Mn(II) using laccases and manganese peroxidases in association with lignocellulose degradation, the mechanisms by which filamentous Ascomycete fungi oxidize Mn(II) and a physiological role for Mn(II) oxidation in these organisms remain poorly understood. Here we use a combination of chemical and in-gel assays and bulk mass spectrometry to demonstrate secretome-based Mn(II) oxidation in three phylogenetically diverse Ascomycetes that is mechanistically distinct from hyphal-associated Mn(II) oxidation on solid substrates. We show that Mn(II) oxidative capacity of these fungi is dictated by species-specific secreted enzymes and varies with secretome age, and we reveal the presence of both Cu-based and FAD-based Mn(II) oxidation mechanisms in all 3 species, demonstrating mechanistic redundancy. Specifically, we identify candidate Mn(II)-oxidizing enzymes as tyrosinase and glyoxal oxidase in Stagonospora sp. SRC1lsM3a, bilirubin oxidase in Stagonospora sp. and Paraconiothyrium sporulosum AP3s5-JAC2a, and GMC oxidoreductase in all 3 species, including Pyrenochaeta sp. DS3sAY3a. The diversity of the candidate Mn(II)-oxidizing enzymes identified in this study suggests that the ability of fungal secretomes to oxidize Mn(II) may be more widespread than previously thought.

Laccase-catalyzed oxidative cross-linking of tyrosine and potato patatin- and lysozyme-derived peptides: Molecular and kinetic study

Laccase can catalyze the oxidative cross-linking of peptides, which is useful in the production of proteinaceous materials with enhanced functional properties. However, the kinetics and the pathway of this reaction remain unclear. In the present study, laccase-catalyzed oxidative cross-linking reaction was investigated through a combination of computational analysis, kinetic studies and end-product profiling using selected substrate models, including peptide AG-10 (AKKIVSDGNG) (without tyrosine) derived from lysozyme and tyrosine-containing peptide ST-10 (SYMTDYYLST) from potato protein (patatin), and tyrosine. Both laccases from Trametes versicolor (LacTv) and Coriolus hirsutus (LacCh) were used as biocatalysts. Laccase exhibited higher binding affinity and catalytic efficiency (k_cat/K_m) towards ST-10 and AG-10 than tyrosine. Among the laccases, LacCh showed higher k_cat towards the substrate models than LacTv. Through the molecular docking, this result was attributed to the presence of the ASN206 at the cavity of LacCh. The end product profiles reveal the formation of homo-oligomers (> 5 units) of ST-10 in the reaction catalyzed by LacTv, while polymerization was favored by LacCh. These cross-linked products were identified to have a mix of oligo-tyrosine linkages. In contrast, the cross-linking of AG-10 required the presence of ferulic acid as mediator, which resulted in the formation of hetero-oligomers and polymers of AG-10. The knowledge obtained in the present study provide insight into an effective reaction for peptide cross-linking.

Linear Polymerization of Protein by Sterically Controlled Enzymatic Cross-Linking with a Tyrosine-Containing Peptide Loop

The structure of a protein complex needs to be controlled appropriately to maximize its functions. Herein, we report the linear polymerization of bacterial alkaline phosphatase (BAP) through the site-specific cross-linking reaction catalyzed by Trametes sp. laccase (TL). We introduced a peptide loop containing a tyrosine (Y-Loop) to BAP, and the Y-Looped BAP was treated with TL. The Y-Looped BAP formed linear polymers, whereas BAP fused with a C-terminal peptide containing a tyrosine (Y-tag) showed an irregular shape after TL treatment. The sterically confined structure of the Y-Loop could be responsible for the formation of linear BAP polymers. TL-catalyzed copolymerization of Y-Looped BAP and a Y-tagged chimeric antibody-binding protein, pG₂pA-Y, resulted in the formation of linear bifunctional protein copolymers that could be employed as protein probes in an enzyme-linked immunosorbent assay (ELISA). Copolymers comprising Y-Looped BAP and pG₂pA-Y at a molar ratio of 100:1 exhibited the highest signal in the ELISA with 26- and 20-fold higher than a genetically fused chimeric protein, BAP-pG₂pA-Y, and its polymeric form, respectively. This result revealed that the morphology of the copolymers was the most critical feature to improve the functionality of the protein polymers as detection probes, not only for immunoassays but also for other diagnostic applications.

Laccase-Mediated Catalyzed Fluorescent Reporter Deposition for Live-Cell Imaging

Catalyzed reporter deposition (CARD) is a widely established method for labeling biological samples analyzed using microscopy. Horseradish peroxidase, commonly used in CARD to amplify reporter signals, requires the addition of hydrogen peroxide, which may perturb samples used in live-cell microscopy. Herein we describe an alternative method of performing CARD using a laccase enzyme, which does not require exogenous hydrogen peroxide. Laccase is an oxidative enzyme which can carry out single-electron oxidations of phenols and related compounds by reducing molecular oxygen. We demonstrate proof-of-concept for this technique through the nontargeted covalent labeling of bovine serum albumin using a fluorescently labeled ferulic acid derivative as the laccase reporter substrate. We further demonstrate the viability of this approach by performing live-cell CARD with an antibody-conjugated laccase against a surface-bound target. CARD using laccase produces an amplified fluorescence signal by labeling cells without the need for exogenous hydrogen peroxide.

Functionalization of hydrophobic surfaces with antimicrobial peptides immobilized on a bio-interfactant layer

The design of functionalized polymer surfaces using bioactive compounds has grown rapidly over the past decade within many industries including biomedical, textile, microelectronics, bioprocessing and food packaging sectors. Polymer surfaces such as polystyrene (PS) must be treated using surface activation processes prior to the attachment of bioactive compounds. In this study, a new peptide immobilization strategy onto hydrocarbonaceus polymer surfaces is presented. A bio-interfactant layer made up of a tailored combination of laccase from trametes versicolor enzyme and maltodextrin is applied to immobilize peptides. Using this strategy, immobilization of the bio-inspired peptide KLWWMIRRWG-bromophenylalanine-3,4-dihydroxyphenylalanine-G and KLWWMIRRWG-bromophenylalanine-G on polystyrene (PS) was achieved. The interacting laccase layers allows to immobilize antimicrobial peptides avoiding the chemical modification of the peptide with a spacer and providing some freedom that facilitates different orientations. These are not strongly dominated by the substrate as it is the case on hydrophobic surfaces; maintaining the antimicrobial activity. Films exhibited depletion efficiency with respect to the growth of Escherichia coli bacteria and did not show cytotoxicity for fibroblast L929. This environmentally friendly antimicrobial surface treatment is both simple and fast, and employs aqueous solutions. Furthermore, the method can be extended to three-dimensional scaffolds as well as rough and patterned substrates.

A bio-interfactant layer is applied on hydrophobic surfaces to immobilize antimicrobial peptides.

Protein Chemical Labeling Using Biomimetic Radical Chemistry

Chemical labeling of proteins with synthetic low-molecular-weight probes is an important technique in chemical biology. To achieve this, it is necessary to use chemical reactions that proceed rapidly under physiological conditions (i.e., aqueous solvent, pH, low concentration, and low temperature) so that protein denaturation does not occur. The radical reaction satisfies such demands of protein labeling, and protein labeling using the biomimetic radical reaction has recently attracted attention. The biomimetic radical reaction enables selective labeling of the C-terminus, tyrosine, and tryptophan, which is difficult to achieve with conventional electrophilic protein labeling. In addition, as the radical reaction proceeds selectively in close proximity to the catalyst, it can be applied to the analysis of protein–protein interactions. In this review, recent trends in protein labeling using biomimetic radical reactions are discussed.

Analysis of the laccase gene family and miR397-/miR408-mediated posttranscriptional regulation in Salvia miltiorrhiza

Salvia miltiorrhiza is one of the most commonly used traditional Chinese medicine materials. It contains important bioactive phenolic compounds, such as salvianolic acids, flavonoids and anthocyanins. Elucidation of phenolic compound biosynthesis and its regulatory mechanism is of great significance for S. miltiorrhiza quality improvement. Laccases (LACs) are multicopper-containing enzymes potentially involved in the polymerization of phenolic compounds. So far, little has been known about LAC genes in S. miltiorrhiza. Through systematic investigation of the whole genome sequence and transcriptomes of S. miltiorrhiza, we identified 65 full-length SmLAC genes (SmLAC1–SmLAC65). Phylogenetic analysis showed that 62 of the identified SmLACs clustered with LACs from Arabidopsis and Populus trichocarpa in seven clades (C1–C7), whereas the other three fell into one S. miltiorrhiza-specific clade (C8). All of the deduced SmLAC proteins contain four conserved signature sequences and three typical Cu-oxidase domains, and gene structures of most LACs from S. miltiorrhiza, Arabidopsis and P. trichocarpa were highly conserved, however SmLACs encoding C8 proteins showed distinct intron-exon structures. It suggests the conservation and diversity of plant LACs in gene structures. The majority of SmLACs exhibited tissue-specific expression patterns, indicates manifold functions of SmLACs played in S. miltiorrhiza. Analysis of high-throughput small RNA sequences and degradome data and experimental validation using the 5′ RACE method showed that 23 SmLACs were targets of Smi-miR397. Among them, three were also targeted by Smi-miR408. It suggests the significance of miR397 and miR408 in posttranscriptional regulation of SmLAC genes. Our results provide a foundation for further demonstrating the functions of SmLACs in the production of bioactive phenolic compounds in S. miltiorrhiza.

Physico-Chemical Properties of Sugar Beet Pectin-Sodium Caseinate Conjugates via Different Interaction Mechanisms

Polysaccharides and proteins are frequently conjugated through electrostatic attraction, enzymatic cross-linking, and heat treatment (Maillard reaction) to obtain food structuring ingredients, mostly for their application as emulsifiers. The conjugate partners and their interaction type affect performance at acidic or neutral pH and during thermal processing, thus requiring careful selection. Here, the aggregate properties (particle size, conjugate charge, shear viscosity) of three types of sugar beet pectin (SBP)-sodium caseinate (SC) 1:1 conjugates, at acidic and neutral pH (4.5; 7), as well as their thermal processing stability (80 °C), were investigated. The enzymatically cross-linked SBP:SC was more acid tolerant than the electrostatically interacting conjugates. Maillard cross-linked conjugates aggregated at pH 4.5, suggesting poor emulsifier performance in acidic conditions. At pH 7, the three conjugate types showed similar aggregate properties. The results are discussed in terms of structural re-arrangement.

Miranda B, Lodoso-Torrecilla I, van Nisselroy CAJ, Hoogenberg BJ, Dantuma S, Hollmann F, de Vries JW, Warszawik EM, Fischer R, Commandeur U, van Rijn P. Biocatalytically induced surface modification of the tobacco mosaic virus and the bacteriophage M13

A one-step laccase induced free radical oxidation of the tobacco mosaic virus and bacteriophage M13 led to acrylate-functionalized viruses with customizable properties.

A comparative structural analysis of the surface properties of asco-laccases

Laccases of different biological origins have been widely investigated and these studies have elucidated fundamentals of the generic catalytic mechanism. However, other features such as surface properties and residues located away from the catalytic centres may also have impact on enzyme function. Here we present the crystal structure of laccase from Myceliophthora thermophila (MtL) to a resolution of 1.62 Å together with a thorough structural comparison with other members of the CAZy family AA1_3 that comprises fungal laccases from ascomycetes. The recombinant protein produced in A. oryzae has a molecular mass of 75 kDa, a pI of 4.2 and carries 13.5 kDa N-linked glycans. In the crystal, MtL forms a dimer with the phenolic substrate binding pocket blocked, suggesting that the active form of the enzyme is monomeric. Overall, the MtL structure conforms with the canonical fold of fungal laccases as well as the features specific for the asco-laccases. However, the structural comparisons also reveal significant variations within this taxonomic subgroup. Notable differences in the T1-Cu active site topology and polar motifs imply molecular evolution to serve different functional roles. Very few surface residues are conserved and it is noticeable that they encompass residues that interact with the N-glycans and/or are located at domain interfaces. The N-glycosylation sites are surprisingly conserved among asco-laccases and in most cases the glycan displays extensive interactions with the protein. In particular, the glycans at Asn88 and Asn210 appear to have evolved as an integral part of the asco-laccase structure. An uneven distribution of the carbohydrates around the enzyme give unique properties to a distinct part of the surface of the asco-laccases which may have implication for laccase function–in particular towards large substrates.

Whey protein isolate with improved film properties through cross-linking catalyzed by small laccase from Streptomyces coelicolor

BACKGROUND

The effects of small laccase (SLAC) from Streptomyces coelicolor on the properties of whey protein isolate (WPI) films were studied.

RESULTS

WPI was catalyze by SLAC without phenolic acid assistance. Particle size distribution results showed that some complexes with higher relative molecular weight formed in WPI samples treated with SLAC. The content of α-helixes decreased while those of β-sheets and random coils increased following SLAC treatment according to circular dichroism results. Fourier transform infrared spectral analysis suggested that some conformational changes occurred in WPI following SLAC treatment. Analysis of WPI films prepared by casting after SLAC treatment indicated that their film properties were all improved, including mechanical properties, solubility, water vapor, oxygen and carbon dioxide barrier properties, film color, light transmission, transparency and thermal properties. Compared with that of the control film, some obvious differences in the morphology of the WPI films were observed following SLAC treatment. This report demonstrates that laccase can directly catalyze protein cross-linking, which may be useful to improve the performance of protein films.

CONCLUSION

In this study, SLAC was applied to WPI edible film during the film-making process. The results showed that SLAC can catalyze WPI cross-linking without phenolic acid assistance, and WPI film properties were improved after SLAC treatment. © 2018 Society of Chemical Industry.

Laccase From White Rot Fungi Having Significant Role in Food, Pharma, and Other Industries

Laccases (E.C. 1.10.3.2 benzenediol: oxygen oxidoreductase) are an interesting group of N glycosylated multicopper blue oxidase enzymes and the widely studied enzyme having a broad range of substrate specificity of both phenolic and non-phenolic compounds. They are widely found in fungi, bacteria plant, insects, and in lichen. They catalyze the oxidation of various phenolic and non-phenolic compounds, with the concomitant reduction of molecular oxygen to water. They could increase productivity, efficiency, and quality of products without a costly investment. This chapter depicts the applications of laccase enzyme from white rot fungi, having various industrial (such as textile dye bleaching, paper and pulp bleaching, food includes the baking, it also utilized in fruit juice industry to improve the quality and stabilization of some perishable products having plant oils), pharmaceutical (as it has potential for the synthesis of several useful drugs such anticancerous, antioxidants, synthesis of hormone derivatives because of their high value of oxidation potential) significance.

Electrodeposited gels prepared from protein alloys

AIM

Silk-tropoelastin alloys, composed of recombinant human tropoelastin and regenerated Bombyx mori silk fibroin, are an emerging, versatile class of biomaterials endowed with tunable combinations of physical and biological properties. Electrodeposition of these alloys provides a programmable means to assemble functional gels with both spatial and temporal controllability.

MATERIALS & METHODS

Tropoelastin-modified silk was prepared by enzymatic coupling between tyrosine residues. Hydrogel coatings were electrodeposited using two wire electrodes.

RESULTS & DISCUSSION

Mechanical characterization and in vitro cell culture revealed enhanced adhesive capability and cellular response of these alloy gels as compared with electrogelled silk alone.

CONCLUSION

These electro-depositable silk-tropoelastin alloys constitute a suitable coating material for nanoparticle-based drug carriers and offer a novel opportunity for on-demand encapsulation/release of nanomedicine.

How to enjoy laccases

An analysis of the scientific literature published in the last 10 years reveals a constant growth of laccase applicative research in several industrial fields followed by the publication of a great number of patents. The Green Chemistry journal devoted the cover of its September 2014 issue to a laccase as greener alternative for chemical oxidation. This indicates that laccase "never-ending story" has found a new promising trend within the constant search for efficient (bio)catalysts able to meet the 12 green chemistry principles. A survey of ancient and cutting-edge uses of laccase in different industrial sectors is offered in this review with the aim both to underline their potential and to provide inspiration for new ones. Applications in textile and food fields have been deeply described, as well as examples concerning polymer synthesis and laccase-catalysed grafting. Recent applications in pharmaceutical and cosmetic industry have also been reviewed.

Unraveling the effects of laccase treatment on enzymatic hydrolysis of steam-exploded wheat straw

Laccase enzymes are promising detoxifying agents during lignocellulosic bioethanol production from wheat straw. However, they affect the enzymatic hydrolysis of this material by lowering the glucose recovery yields. This work aimed at explaining the negative effects of laccase on enzymatic hydrolysis. Relative glucose recovery in presence of laccase (10IU/g substrate) with model cellulosic substrate (Sigmacell) at 10% (w/v) was almost 10% points lower (P<0.01) than in the absence of laccase. This fact could be due to an increase in the competition of cellulose binding sites between the enzymes and a slight inhibition of β-glucosidase activity. However, enzymatic hydrolysis and infrared spectra of laccase-treated and untreated wheat straw filtered pretreated residue (WS-FPR), revealed that a grafting process of phenoxy radicals onto the lignin fiber could be the cause of diminished accessibility of cellulases to cellulose in pretreated wheat straw.

The design of dextran-based hypoxia-inducible hydrogels via in situ oxygen-consuming reaction

Hypoxia plays a critical role in the development and wound healing process, as well as a number of pathological conditions. Here, dextran-based hypoxia-inducible (Dex-HI) hydrogels formed with in situ oxygen consumption via a laccase-medicated reaction are reported. Oxygen levels and gradients were accurately predicted by mathematical simulation. It is demonstrated that Dex-HI hydrogels provide prolonged hypoxic conditions up to 12 h. The Dex-HI hydrogel offers an innovative approach to delineate not only the mechanism by which hypoxia regulates cellular responses, but may facilitate the discovery of new pathways involved in the generation of hypoxic and oxygen gradient environments.

Versatile peroxidase as a valuable tool for generating new biomolecules by homogeneous and heterogeneous cross-linking

The modification and generation of new biomolecules intended to give higher molecular-mass species for biotechnological purposes, can be achieved by enzymatic cross-linking. The versatile peroxidase (VP) from Pleurotus eryngii is a high redox-potential enzyme with oxidative activity on a wide variety of substrates. In this study, VP was successfully used to catalyze the polymerization of low molecular mass compounds, such as lignans and peptides, as well as larger macromolecules, such as protein and complex polysaccharides. Different analytical, spectroscopic, and rheological techniques were used to determine structural changes and/or variations of the physicochemical properties of the reaction products. The lignans secoisolariciresinol and hydroxymatairesinol were condensed by VP forming up to 8 unit polymers in the presence of organic co-solvents and Mn(2+). Moreover, 11 unit of the peptides YIGSR and VYV were homogeneously cross-linked. The heterogeneous cross-linking of one unit of the peptide YIGSR and several lignan units was also achieved. VP could also induce gelation of feruloylated arabinoxylan and the polymerization of β-casein. These results demonstrate the efficacy of VP to catalyze homo- and hetero-condensation reactions, and reveal its potential exploitation for polymerizing different types of compounds.