Heterologous production and characterization of chitin deacetylases with chitin binding domains

Chitin Deacetylasen (CDAs) katalysieren die Acetamido-Hydrolyse von N-Acetylglucosamin zu Glucosamin in Chitin und Chitosan. Es ist nachgewiesen, dass chemisch produzierte Chitosane ein zufälliges Acetylierungsmuster (PA) aufweisen, welches wahrscheinlich die biologische Aktivität und damit die Anwendung des Polymers beeinflusst. Thema dieser Arbeit ist die Charakterisierung zweier pilzlicher CDAs (BC95 aus Botrytis cinerea und PaCDA aus Podospora anserina), welche zusätzlich zur katalytischen Domäne Chitin-Bindedomänen (CBDs) aufweisen. Die heterologe Produktion beider Enzyme wurde erfolgreich in der Hefe Hansenula polymorpha durchgeführt, jedoch zeigte nur PaCDA Enzymaktivität. Des Weiteren wurden Deletionsvarianten der PaCDA erstellt, um die Rolle der CBDs zu untersuchen. Die Wirkungsweise von PaCDA wurde anhand der Produkte analysiert und ist nicht prozessiv; dennoch produziert das Enzym ein spezifisches Acetylierungsmuster, welches durch alternierende Einheiten gekennzeichnet istChitin deacetylases (CDAs) catalyze the acetamido hydrolysis of N-acetylglucosamine to glucosamine in chitin and chitosan. It has been demonstrated that chemically produced chitosans show a random pattern of acetylation (PA), which is supposed to influence the biological activity and thereby the application of the polymer. The subject of this study is the characterization of two fungal CDAs (BC95 from Botrytis cinerea and PaCDA from Podospora anserina), which possess additional chitin binding domains (CBDs) next to the catalytic domain. The heterologous production of both enzymes was successful in Hansenula polymorpha, but CDA activity was confirmed only for PaCDA. Additionally, deletion variants of PaCDA were constructed to analyze the role of the CBDs. The mode of action of PaCDA was determined by product analysis and is not processive; nevertheless the enzyme is producing a specific PA, which is characterized by alternating uni

Structural and biochemical characterization of the exopolysaccharide deacetylase Agd3 required for Aspergillus fumigatus biofilm formation

The exopolysaccharide galactosaminogalactan (GAG) is an important virulence factor of the fungal pathogen Aspergillus fumigatus. Deletion of a gene encoding a putative deacetylase, Agd3, leads to defects in GAG deacetylation, biofilm formation, and virulence. Here, we show that Agd3 deacetylates GAG in a metal-dependent manner, and is the founding member of carbohydrate esterase family CE18. The active site is formed by four catalytic motifs that are essential for activity. The structure of Agd3 includes an elongated substrate-binding cleft formed by a carbohydrate binding module (CBM) that is the founding member of CBM family 87. Agd3 homologues are encoded in previously unidentified putative bacterial exopolysaccharide biosynthetic operons and in other fungal genomes. The exopolysaccharide galactosaminogalactan (GAG) is an important virulence factor of the fungal pathogen Aspergillus fumigatus. Here, the authors study an A. fumigatus enzyme that deacetylates GAG in a metal-dependent manner and constitutes a founding member of a new carbohydrate esterase family.Bio-organic Synthesi

A systematic review of the literature on digital transformation: insights and implications for strategy and organizational change

In this article we provide a systematic review of the extensive yet diverse and fragmented literature on digital transformation (DT), with the goal of clarifying boundary conditions to investigate the phenomenon from the perspective of organizational change. On the basis of 279 articles, we provide a multi-dimensional framework synthesizing what is known about DT and discern two important thematical patterns: DT is moving firms to malleable organizational designs that enable continuous adaptation, and this move is embedded in and driven by digital business ecosystems. From these two patterns, we derive four perspectives on the phenomenon of DT: technology impact, compartmentalized adaptation, systemic shift and holistic co-evolution. Linking our findings and interpretations to existing work, we find that the nature of DT is only partially covered by conventional frameworks on organizational change. On the basis of this analysis, we derive a research agenda and provide managerial implications for strategy and organizational change.info:eu-repo/semantics/publishedVersio

Asymmetrically Substituted Tetrahedral Cobalt NHC Complexes and Their Use as ALD as well as Low-Temperature CVD Precursors

The synthesis of novel asymmetrically substituted cobalt complexes of the type [Co­(CO)­(NO)­(NHC)­(PR₃)] (NHC = ^<i>i</i>Pr₂Im, PR₃ = PMe₃ (<b>1</b>), PEt₃(<b>2</b>), PH^<i>i</i>Pr₂ (<b>3</b>); PR₃ = PMe₃;, NHC = Me₂Im^Me (<b>4</b>), Me^<i>i</i>PrIm (<b>5</b>), Me^<i>t</i>BuIm (<b>6</b>), ^<i>i</i>Pr₂Im^Me (<b>7</b>); R₂Im = 1,3-dialkylimidazolin-2-ylidene) is reported. These complexes are stabilized by N-heterocyclic carbene (NHC), phosphine, carbonyl, and nitrosyl ligands and have been synthesized from the reaction of a NHC-substituted precursor of the type [Co­(CO)₂(NO)­(NHC)] and the corresponding phosphine. The synthesis of [Co­(CO)­(NO)­(Me^<i>t</i>BuIm)­(PMe₃)] (<b>6</b>) and [Co­(CO)­(NO)­(^<i>i</i>Pr₂Im^Me)­(PMe₃)] (<b>7</b>) proceeds in a thermal reaction even at room temperature by quantitative replacement of one carbonyl with a phosphine ligand. All of the other complexes were synthesized using photochemical conditions. Complexes <b>1</b>–<b>6</b> have been characterized by elemental analysis, IR spectroscopy, and multinuclear NMR spectroscopy and in some cases by X-ray crystallography. All complexes are volatile, are stable upon sublimation, and decompose readily in a stepwise manner at elevated temperature. The complex [Co­(CO)­(NO)­(^<i>i</i>Pr₂Im)­(PMe₃)] (<b>1</b>) as well as cobalt complexes that were reported earlier, i.e. [Co­(CO)­(NO)­(^<i>i</i>Pr₂Im)₂], [Co­(CO)­(NO)­(Me^<i>t</i>BuIm)₂], and [Co­(CO)₂(NO)­(^<i>i</i>Pr₂Im)], are evaluated and have been successfully applied in the deposition of cobalt-based thin films