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Instruments / Technical Area	Publication Details	Published
I24-Microfocus Macromolecular Crystallography	Structural analysis and biochemical properties of laccase enzymes from two Pediococcus species Isidoro Olmeda , Patricia Casino , Robert E. Collins , Ramón Sendra , Sara Callejón , Juanjo Huesa , Alexei S. Soares , Sergi Ferrer , Isabel Pardo Microbial Biotechnology 9 DOI: 10.1111/1751-7915.13751 Diamond Proposal Number(s): [14739, 20229] Open Access Show Abstract ▼ Abstract: Prokaryotic laccases are emergent biocatalysts. However, they have not been broadly found and characterized in bacterial organisms, especially in lactic acid bacteria. Recently, a prokaryotic laccase from the lactic acid bacterium Pediococcus acidilactici 5930, which can degrade biogenic amines, was discovered. Thus, our study aimed to shed light on laccases from lactic acid bacteria focusing on two Pediococcus laccases, P. acidilactici 5930 and Pediococcus pentosaceus 4816, which have provided valuable information on their biochemical activities on redox mediators and biogenic amines. Both laccases are able to oxidize canonical substrates as ABTS, ferrocyanide and 2,6‐DMP, and non‐conventional substrates as biogenic amines. With ABTS as a substrate, they prefer an acidic environment and show sigmoidal kinetic activity, and are rather thermostable. Moreover, this study has provided the first structural view of two lactic acid bacteria laccases, revealing new structural features not seen before in other well‐studied laccases, but which seem characteristic for this group of bacteria. We believe that understanding the role of laccases in lactic acid bacteria will have an impact on their biotechnological applications and provide a framework for the development of engineered lactic acid bacteria with enhanced properties.	Feb 2021
I03-Macromolecular Crystallography	Characterization and engineering of a two-enzyme system for plastics depolymerization Brandon C. Knott , Erika Erickson , Mark D. Allen , Japheth E. Gado , Rosie Graham , Fiona L. Kearns , Isabel Pardo , Ece Topuzlu , Jared Anderson , Harry P. Austin , Graham Dominick , Christopher W. Johnson , Nicholas A. Rorrer , Caralyn J. Szostkiewicz , Valérie Copié , Christina M. Payne , H. Lee Woodcock , Bryon S. Donohoe , Gregg T. Beckham , John E. Mcgeehan Proceedings Of The National Academy Of Sciences DOI: 10.1073/pnas.2006753117 Diamond Proposal Number(s): [17212] Open Access Show Abstract ▼ Abstract: Plastics pollution represents a global environmental crisis. In response, microbes are evolving the capacity to utilize synthetic polymers as carbon and energy sources. Recently, Ideonella sakaiensis was reported to secrete a two-enzyme system to deconstruct polyethylene terephthalate (PET) to its constituent monomers. Specifically, the I. sakaiensis PETase depolymerizes PET, liberating soluble products, including mono(2-hydroxyethyl) terephthalate (MHET), which is cleaved to terephthalic acid and ethylene glycol by MHETase. Here, we report a 1.6 Å resolution MHETase structure, illustrating that the MHETase core domain is similar to PETase, capped by a lid domain. Simulations of the catalytic itinerary predict that MHETase follows the canonical two-step serine hydrolase mechanism. Bioinformatics analysis suggests that MHETase evolved from ferulic acid esterases, and two homologous enzymes are shown to exhibit MHET turnover. Analysis of the two homologous enzymes and the MHETase S131G mutant demonstrates the importance of this residue for accommodation of MHET in the active site. We also demonstrate that the MHETase lid is crucial for hydrolysis of MHET and, furthermore, that MHETase does not turnover mono(2-hydroxyethyl)-furanoate or mono(2-hydroxyethyl)-isophthalate. A highly synergistic relationship between PETase and MHETase was observed for the conversion of amorphous PET film to monomers across all nonzero MHETase concentrations tested. Finally, we compare the performance of MHETase:PETase chimeric proteins of varying linker lengths, which all exhibit improved PET and MHET turnover relative to the free enzymes. Together, these results offer insights into the two-enzyme PET depolymerization system and will inform future efforts in the biological deconstruction and upcycling of mixed plastics.	Sep 2020
I02-Macromolecular Crystallography	Advanced synthesis of conductive polyaniline using laccase as biocatalyst Felipe De Salas , Isabel Pardo , Horacio J. Salavagione , Pablo Aza , Eleni Amougi , Jesper Vind , Angel T. Martínez , Susana Camarero Plos One 11 DOI: 10.1371/journal.pone.0164958 Open Access Show Abstract ▼ Abstract: Polyaniline is a conductive polymer with distinctive optical and electrical properties. Its enzymatic synthesis is an environmentally friendly alternative to the use of harsh oxidants and extremely acidic conditions. 7D5L, a high-redox potential laccase developed in our lab, is the biocatalyst of choice for the synthesis of green polyaniline (emeraldine salt) due to its superior ability to oxidize aniline and kinetic stability at the required polymerization conditions (pH 3 and presence of anionic surfactants) as compared with other fungal laccases. Doses as low as 7.6 nM of 7D5L catalyze the polymerization of 15 mM aniline (in 24 h, room temperature, 7% yield) in the presence of different anionic surfactants used as doping templates to provide linear and water-soluble polymers. Aniline polymerization was monitored by the increase of the polaron absorption band at 800 nm (typical for emeraldine salt). Best polymerization results were obtained with 5 mM sodium dodecylbenzenesulfonate (SDBS) as template. At fixed conditions (15 mM aniline and 5mM SDBS), polymerization rates obtained with 7D5L were 2.5-fold the rates obtained with commercial Trametes villosa laccase. Moreover, polyaniline yield was notably boosted to 75% by rising 7D5L amount to 0.15 μM, obtaining 1g of green polyaniline in 1L-reaction volume. The green polymer obtained with the selected system (7D5L/SDBS) holds excellent electrochemical and electro-conductive properties displayed in water-dispersible nanofibers, which is advantageous for the nanomaterial to be readily cast into uniform films for different applications.	Oct 2016

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