Engineering and Applications of fungal laccases for organic synthesis

Laccases are multi-copper containing oxidases (EC 1.10.3.2), widely distributed in fungi, higher plants and bacteria. Laccase catalyses the oxidation of phenols, polyphenols and anilines by one-electron abstraction, with the concomitant reduction of oxygen to water in a four-electron transfer process. In the presence of small redox mediators, laccase offers a broader repertory of oxidations including non-phenolic substrates. Hence, fungal laccases are considered as ideal green catalysts of great biotechnological impact due to their few requirements (they only require air, and they produce water as the only by-product) and their broad substrate specificity, including direct bioelectrocatalysis

Enzymatic synthesis and characterization of different families of chitooligosaccharides and their bioactive properties

Chitooligosaccharides (COS) are homo- or hetero-oligomers of D-glucosamine (GlcN) and N-acetyl-D-glucosamine (GlcNAc) that can be obtained by chitosan or chitin hydrolysis. Their enzymatic production is preferred over other methodologies (physical, chemical, etc.) due to the mild conditions required, the fewer amounts of waste and its efficiency to control product composition. By properly selecting the enzyme (chitinase, chitosanase or nonspecific enzymes) and the substrate properties (degree of deacetylation, molecular weight, etc.), it is possible to direct the synthesis towards any of the three COS types: fully acetylated (faCOS), partially acetylated (paCOS) and fully deacetylated (fdCOS). In this article, we review the main strategies to steer the COS production towards a specific group. The chemical characterization of COS by advanced techniques, e.g., high-performance anion-exchange chromatography with pulsed amperometric detection (HPAECPAD) and MALDI-TOF mass spectrometry, is critical for structure-function studies. The scaling of processes to synthesize specific COS mixtures is difficult due to the low solubility of chitin/chitosan, the heterogeneity of the reaction mixtures, and high amounts of salts. Enzyme immobilization can help to minimize such hurdles. The main bioactive properties of COS are herein reviewed. Finally, the anti-inflammatory activity of three COS mixtures was assayed in murine macrophages after stimulation with lipopolysaccharidesThis work was supported by grants from the EU EMFF-Blue Economy-2018 (FISH4FISH- 863697 project), the Spanish Ministry of Economy and Competitiveness (Grants BIO2016-76601- C3-1,2-R), the Spanish Ministry of Science and Innovation (Grants PID2019-105838RB-C31/C32), Fundación Ramón Areces (XIX Call of Research Grants in Life and Material Sciences) and by an institutional grant from Fundación Ramón Areces to the Centro de Biología Molecula

Synthesis of 1‐Naphthol by a Natural Peroxygenase engineered by Directed Evolution

This is the peer reviewed version of the following article, which has been published in final form at 10.1002/cbic.201500493. This article may be used for non-commercial purposes in accordance With Wiley-VCH Terms and Conditions for self-archivingThere is an increasing interest in enzymes that catalyze the hydroxylation of naphthalene under mild conditions and with minimal requirements. To address this challenge, an extracellular fungal aromatic peroxygenase with mono(per)oxygenase activity was engineered to convert naphthalene selectively into 1-naphthol. Mutant libraries constructed by random mutagenesis and DNA recombination were screened for peroxygenase activity on naphthalene together with quenching of the undesired peroxidative activity on 1-naphthol (one-electron oxidation). The resulting double mutant (G241D-R257K) obtained from this process was characterized biochemically and computationally. The conformational changes produced by directed evolution improved the substrate's catalytic position. Powered exclusively by catalytic concentrations of H2O2, this soluble and stable biocatalyst has a total turnover number of 50 000, with high regioselectivity (97 %) and reduced peroxidative activity.We thank Paloma Santos Moriano (ICP, CSIC, Spain) for assistance with the HPLC and LC/MS analysis, and Jesper Vind (Novozymes, Denmark) and Angel T. Martinez (CIB, CSIC, Spain) for helpful discussions. This work was supported by the European Commission projects Indox-FP7-KBBE-2013-7-613549 and Cost-Action CM1303-Systems Biocatalysis, and the National Projects Dewry [BIO201343407-R], Cambios [RTC-2014-1777-3] and OXYdesign [CTQ2013-48287-R].Peer ReviewedPostprint (author's final draft

Molecular characterization and heterologous expression of a Xanthophyllomyces dendrorhous ¿-glucosidase with potential for prebiotics production

Abstract Basidiomycetous yeast Xanthophyllomyces dendrorhous expresses an α-glucosidase with strong transglycosylation activity producing prebiotic sugars such as panose and an unusual tetrasaccharides mixture including α–(1–6) bonds as major products, which makes it of biotechnological interest. Initial analysis pointed to a homodimeric protein of 60 kDa subunit as responsible for this activity. In this study, the gene Xd-AlphaGlu was characterized. The 4131-bp-long gene is interrupted by 13 short introns and encodes a protein of 990 amino acids (Xd-AlphaGlu). The N-terminal sequence of the previously detected 60 kDa protein resides in this larger protein at residues 583–602. Functionality of the gene was proved in Saccharomyces cerevisiae, which produced a protein of about 130 kDa containing Xd-AlphaGlu sequences. All properties of the heterologously expressed protein, including thermal and pH profiles, activity on different substrates, and ability to produce prebiotic sugars were similar to that of the α-glucosidase produced in X. dendrorhous. No activity was detected in S. cerevisiae containing exclusively the 1256-bp from gene Xd-AlphaGlu that would encode synthesis of the 60 kDa protein previously detected. Data were compatible with an active monomeric α-glucosidase of 990 amino acids and an inactive hydrolysis product of 60 kDa. Protein Xd-AlphaGlu contained most of the elements characteristic of α-glucosidases included in the glycoside hydrolases family GH31 and its structural model based on the homologous human maltase-lucoamylase was obtained. Remarkably, the Xd-AlphaGlu C-terminal domain presents an unusually long 115-residue insertion that could be involved in this enzyme’s activity against long-size substrates such as maltoheptaose and soluble starch.Spanish Ministry of Economy and Competitiveness supported this research. We thank Fundación Ramón Areces for the institutional grant to the Centro de Biología Molecular Severo OchoaPeer Reviewe

Modulating the Synthesis of Dextran with the Acceptor Reaction Using Native and Encapsulated Dextransucrases

Dextransucrases are glucansucrases with broad applications in the food, cosmetics and pharmaceutical industries. Using sucrose as the glucosyl donor, they synthesize both high molecular weight (HMW) dextrans and potential prebiotic oligosaccharides. The process selectivity can be modulated by varying the reaction conditions. When no other molecule is present in the reaction, only dextrans are synthesized. In the presence of methyl α-D-glucopyranoside, the synthesis of methyl polyglucosides takes place, diminishing the transfer of glucose molecules to form dextran. In this work, the formation of HMW soluble dextran and methyl polyglucosides was studied with dextransucrases from Leuconostoc mesenteroides, strains B-512F and B-1299. The amount of dextran formed with dextransucrase B-512F was reduced up to 4 % with respect to the control in absence of acceptor, using a mass ratio of sucrose:methyl α-D-glucopyranoside of 1:4. The encapsulation in alginate retains the dextran inside the beads, causing a distortion of the biocatalyst and finally releasing the polysaccharides into the reaction medium

Isomelezitose overproduction by alginate-entrapped recombinant E. coli cells and In vitro evaluation of its potential prebiotic effect

In this work, the trisaccharide isomelezitose was overproduced from sucrose using a biocatalyst based on immobilized Escherichia coli cells harbouring the α-glucosidase from the yeast Metschnikowia reukaufii, the best native producer of this sugar described to date. The overall process for isomelezitose production and purification was performed in three simple steps: (i) oligosaccharides synthesis by alginate-entrapped E. coli; (ii) elimination of monosaccharides (glucose and fructose) using alginate-entrapped Komagataella phaffii cells; and (iii) semi-preparative high performance liquid chromatography under isocratic conditions. As result, approximately 2.15 g of isomelezitose (purity exceeding 95%) was obtained from 15 g of sucrose. The potential prebiotic effect of this sugar on probiotic bacteria (Lactobacillus casei, Lactobacillus rhamnosus and Enterococcus faecium) was analysed using in vitro assays for the first time. The growth of all probiotic bacteria cultures supplemented with isomelezitose was significantly improved and was similar to that of cultures supplemented with a commercial mixture of fructo-oligosaccharides. In addition, when isomelezitose was added to the bacteria cultures, the production of organic acids (mainly butyrate) was significantly promoted. Therefore, these results confirm that isomelezitose is a potential novel prebiotic that could be included in healthier foodstuffs designed for human gastrointestinal balance maintenanc

Reactivity and Applications of Singlet Oxygen Molecule

Reactive oxygen species (ROS) are molecules produced in living organisms, in the environment, and in various chemical reactions. The main species include, among others, singlet oxygen (1O2), the superoxide anion radical (•O2−), the hydroxyl radical (HO•), and the hydroperoxyl radical (HOO•). In general, the reactivity of 1O2 is lower than that of HO• but even higher than that of •O2−. Singlet oxygen is the lowest energy excited state of molecular oxygen, but it is also a highly reactive species, which can initiate oxidation reactions of biomolecules such as amino acids, proteins, nucleic acids, and lipids, either by a direct reaction or by the induction of ROS. Singlet oxygen is a highly reactive electrophilic species that reacts with electron-rich molecules and is related to several types of pathologies. To inhibit the oxidation of biomolecules with this species, some substances act as antioxidants by performing a quenching effect. In this chapter, aspects such as its physicochemical properties, methods of generation and detection, as well as the reactivity of this molecule are detailed

Enzymatic Synthesis of Phloretin alpha-Glucosides Using a Sucrose Phosphorylase Mutant and its Effect on Solubility, Antioxidant Properties and Skin Absorption

Glycosylation of polyphenols may increase their aqueous solubility, stability, bioavailability and pharmacological activity. Herein, we used a mutant of sucrose phosphorylase from Thermoanaerobacterium thermosaccharolyticum engineered to accept large polyphenols (variant TtSPP_R134A) to produce phloretin glucosides. The reaction was performed using 10% (v/v) acetone as cosolvent. The selective formation of a monoglucoside or a diglucoside (53% and 73% maximum conversion percentage, respectively) can be kinetically controlled. MS and 2D-NMR determined that the monoglucoside was phloretin 4¿-O-¿-D-glucopyranoside and the diglucoside phloretin-4¿-O-[¿-D-glucopyranosyl-(1¿3)-O-¿-D-glucopyranoside], a novel compound. The molecular features that determine the specificity of this enzyme for 4¿-OH phenolic group were analysed by induced-fit docking analysis of each putative derivative, using the crystal structure of TtSPP and changing the mutated residue. The mono- and diglucoside were, respectively, 71- and 1200-fold more soluble in water than phloretin at room temperature. The a-glucosylation decreased the antioxidant capacity of phloretin, measured by DPPH and ABTS assays; however, this loss was moderate and the activity could be recovered upon deglycosylation in vivo. Since phloretin attracts a great interest in dermocosmetic applications, we analyzed the percutaneous absorption of glucosides and the aglycon employing a pig skin model. Although the three compounds were detected in all skin layers (except the fluid receptor), the diglucoside was present mainly on superficial layers

Genetically engineered proteins with two active sites for enhanced biocatalysis and synergistic chemo- and biocatalysis

Enzyme engineering has allowed not only the de novo creation of active sites catalysing known biological reactions with rates close to diffusion limits, but also the generation of abiological sites performing new-to-nature reactions. However, the catalytic advantages of engineering multiple active sites into a single protein scaffold are yet to be established. Here, we report on proteins with two active sites of biological and/or abiological origin, for improved natural and non-natural catalysis. The approach increased the catalytic properties, such as enzyme efficiency, substrate scope, stereoselectivity and optimal temperature window, of an esterase containing two biological sites. Then, one of the active sites was metamorphosed into a metal-complex chemocatalytic site for oxidation and Friedel–Crafts alkylation reactions, facilitating synergistic chemo- and biocatalysis in a single protein. The transformations of 1-naphthyl acetate into 1,4-naphthoquinone (conversion approx. 100%) and vinyl crotonate and benzene into 3-phenylbutyric acid (≥83%; e.e. >99.9%) were achieved in one pot with this artificial multifunctional metalloenzyme.This work was funded by grant ‘INMARE’ from the European Union’s Horizon 2020 (grant agreement no. 634486), grants PCIN-2017-078 (within the Marine Biotechnology ERA-NET), CTQ2016-79138-R, BIO2016-76601-C3-1-R, BIO2016-76601-C3-3-R, BIO2017-85522-R, RTI2018-095166-B-I00 and RTI2018-095090-B-100 from the Ministerio de Economía y Competitividad, the Ministerio de Ciencia, Innovación y Universidades (MCIU), the Agencia Estatal de Investigación (AEI), the Fondo Europeo de Desarrollo Regional (FEDER) and the European Union (EU). P.N.G. and R.B. acknowledge the support of the UK Biotechnology and Biological Sciences Research Council (BBSRC; grant No. BB/M029085/1) and the Centre of Environmental Biotechnology Project and the Supercomputing Wales project, which are partly funded by the European Regional Development Fund (ERDF) through the Welsh Government. The authors gratefully acknowledge the financial support provided by the ERDF. C.C. thanks the Ministerio de Economía y Competitividad and FEDER for a Ph.D. fellowship (Grant BES-2015-073829). J.L.G.-A. thanks the support of the Spanish Ministry of Education, Culture and Sport through the National Program FPU (FPU17/00044). I.C.-R. thanks the Regional Government of Madrid for a fellowship (PEJ_BIO_AI_1201). The authors would like to acknowledge S. Ciordia and M. C. Mena for MALDI-TOF/TOF analysis. We thank the staff of both the European Synchrotron Radiation Facility (ESRF, Grenoble, France), for providing access and technical assistance at beamline ID30A-1/MASSIf-1, and the Synchrotron Radiation Source at Alba (Barcelona, Spain), for assistance at BL13-XALOC beamline. The authors would also like to acknowledge M. J. Vicente and M. A. Pascual at the Servicio Interdepartamental de Investigación (SIDI) of the Autonomous University of Madrid for the ESI-MS analyses