Glucuronoyl esterases - enzymes to decouple lignin and carbohydrates and enable better utilization of renewable plant biomass

Glucuronoyl esterases (GEs) are microbial enzymes able to cleave covalent linkages between lignin and carbohydrates in the plant cell wall. GEs are serine hydrolases found in carbohydrate esterase family 15 (CE15), which belongs to the large α/β hydrolase superfamily. GEs have been shown to reduce plant cell wall recalcitrance by hydrolysing the ester bonds found between glucuronic acid moieties on xylan polysaccharides and lignin. In recent years, the exploration of CE15 has broadened significantly and focused more on bacterial enzymes, which are more diverse in terms of sequence and structure to their fungal counterparts. Similar to fungal GEs, the bacterial enzymes are able to improve overall biomass deconstruction but also appear to have less strict substrate preferences for the uronic acid moiety. The structures of bacterial GEs reveal that they often have large inserts close to the active site, with implications for more extensive substrate interactions than the fungal GEs which have more open active sites. In this review, we highlight the recent work on GEs which has predominantly regarded bacterial enzymes, and discuss similarities and differences between bacterial and fungal enzymes in terms of the biochemical properties, diversity in sequence and modularity, and structural variations that have been discovered thus far in CE15

Distributed correlations and information flows within a hybrid multipartite quantum-classical system

Understanding the non-Markovian mechanisms underlying the revivals of quantum entanglement in the presence of classical environments is central in the theory of quantum information. Tentative interpretations have been given by either the role of the environment as a control device or the concept of hidden entanglement. We address this issue from an information-theoretic point of view. To this aim, we consider a paradigmatic tripartite system, already realized in the laboratory, made of two independent qubits and a random classical field locally interacting with one qubit alone. We study the dynamical relationship between the two-qubit entanglement and the genuine tripartite correlations of the overall system, finding that collapse and revivals of entanglement correspond, respectively, to raise and fall of the overall tripartite correlations. Interestingly, entanglement dark periods can enable plateaux of nonzero tripartite correlations. We then explain this behavior in terms of information flows among the different parties of the system. Besides showcasing the phenomenon of the freezing of overall correlations, our results provide new insights on the origin of retrieval of entanglement within a hybrid quantum-classical system.Comment: 9 pages, 5 figures. To appear on Phys. Rev.

Rational engineering of a hyperstable glycosyltransferase for blue denim dyeing

Indigo is one of the most used dyes to produce the textile blue denim worldwide1. Its synthesis and the dyeing process require chemical steps that are environmentally damaging, including the use of reducing agents for indigo solubilization. The glycosyltransferase PtUGT1 is able to add a glucose moiety to the reactive indigo precursor indoxyl to form indican, preventing spontaneous oxidation and keeping it soluble2. This strategy could be used in a chemoenzymatic approach to replace the use of reducing agents, but in order to do this it’s necessary that PtUGT1 resist, and to be active under the harsh conditions used in the industrial process, including high pH and high temperature. We have characterized the activity profile of PtUGT1 at different pH values and temperatures and have determined the enzyme stability by differential scanning fluorometry (DSF) and residual activity. Leveraging the structure information of PtUGT1 obtained by X-ray crystallography (PDB ID: 5nlm)2, we have rationally designed different mutants to develop a variant adapted to higher temperatures and pH values, including hypothetical residue pair mutants that could lead to the formation of intramolecular disulfide bridges, and mutants that could either improve the hydrophobic packing, lead to formation of polar interactions or improve Pro/Gly ratio, consequently increasing the rigidity/stability of PtUGT1. As a result we have developed several active PtUGT1 variants with up to 15°C increase in their melting temperature (TmB) (Fig. 1), the highest ever reported for an UDP-dependent glycosyltransferase. Please click Additional Files below to see the full abstract

Lytic polysaccharide monooxygenases:a crystallographer's view on a new class of biomass-degrading enzymes

Lytic polysaccharide monooxygenases (LPMOs) are a new class of microbial copper enzymes involved in the degradation of recalcitrant polysaccharides. They have only been discovered and characterized in the last 5–10 years and have stimulated strong interest both in biotechnology and in bioinorganic chemistry. In biotechnology, the hope is that these enzymes will finally help to make enzymatic biomass conversion, especially of lignocellulosic plant waste, economically attractive. Here, the role of LPMOs is likely to be in attacking bonds that are not accessible to other enzymes. LPMOs have attracted enormous interest since their discovery. The emphasis in this review is on the past and present contribution of crystallographic studies as a guide to functional understanding, with a final look towards the future

Transitività e alternanze argomentali nell'italiano scritto e parlato: un'indagine empirica.

Il presente lavoro costituisce un'indagine qualitativa, quantitativa e comparativa sulle proprietà di sottocategorizzazione e i significati di 10 verbi italiani ad alternanza transitivo/intransitivo. Il capitolo I fornisce un’introduzione teorica sulle problematiche relative alla struttura e all’alternanza argomentale a partire dalla nozione di valenza elaborata da Tesnière. Sono descritti tre approcci teorici differenti: lessicalista, costruzionista e empirici (linguistica dei corpora). Infine vengono descritti quattro tentativi di classificazione dei verbi italiani sulla base delle strutture e/o delle alternanze argomentali. Il capitolo II si incentra sulle sole alternanze transitivo/intransitivo, oggetto specifico dell’indagine. Vengono presentate le tipologie di alternanze di transitività che si possono riscontrare nella lingua italiana, utilizzando i contributi teorici di studi precedenti, e infine sono descritti tre studi effettuati su corpora sull’argomento specifico, 2 per l’inglese e uno per l’italiano. Il capitolo III è un’introduzione metodologica all’indagine effettuata. Verranno descritti gli obiettivi della ricerca, i materiali utilizzati (il corpus di parlato, il corpus di scritto e i data-base estratti da quest’ultimo), i criteri di selezione dei verbi e il numero totale di occorrenze, le caratteristiche individuate, i criteri e le modalità di annotazione delle singole occorrenze. Nel capitolo IV sono esposti i risultati qualitativi. Esso costituisce un contributo lessicografico sui significati e le strutture morfosintattiche dei verbi esaminati. Infine, il capitolo V contiene i risultati quantitativi, ossia le frequenze relative e assolute delle configurazioni e dei significati individuati per ciascun verbo. I dati relativi a scritto e parlato verranno messi a confronto e verranno rilevate le linee di tendenza riscontrate, le problematiche emerse, le eventuali prospettive di studio per ulteriori indagini

Characterization of different crystal forms of the α-glucosidase MalA from \u3ci\u3eSulfolobus solfataricus\u3c/i\u3e

MalA is an _-glucosidase from the hyperthermophilic archaeon Sulfolobus solfataricus. It belongs to glycoside hydrolase family 31, which includes several medically interesting α-glucosidases. MalA and its selenomethionine derivative have been overproduced in Escherichia coli and crystallized in four different crystal forms. Microseeding was essential for the formation of good-quality crystals of forms 2 and 4. For three of the crystal forms (2, 3 and 4) full data sets could be collected. The most suitable crystals for structure determination are the monoclinic form 4 crystals, belonging to space group P21, from which data sets extending to 2.5 Å resolution have been collected. Self-rotation functions calculated for this form and for the orthorhombic (P212121) form 2 indicate the presence of six molecules in the asymmetric unit related by 32 symmetry

Characterization of different crystal forms of the α-glucosidase MalA from \u3ci\u3eSulfolobus solfataricus\u3c/i\u3e

MalA is an _-glucosidase from the hyperthermophilic archaeon Sulfolobus solfataricus. It belongs to glycoside hydrolase family 31, which includes several medically interesting α-glucosidases. MalA and its selenomethionine derivative have been overproduced in Escherichia coli and crystallized in four different crystal forms. Microseeding was essential for the formation of good-quality crystals of forms 2 and 4. For three of the crystal forms (2, 3 and 4) full data sets could be collected. The most suitable crystals for structure determination are the monoclinic form 4 crystals, belonging to space group P21, from which data sets extending to 2.5 Å resolution have been collected. Self-rotation functions calculated for this form and for the orthorhombic (P212121) form 2 indicate the presence of six molecules in the asymmetric unit related by 32 symmetry