Sulfur containing metabolites are ubiquitous and important factors in all life forms. Deciphering their physiological functions, their chemical reactivity and their biosynthetic origins has proven a productive avenue to identify causes and remedies of human disease, to understand microbial contributions and reactions to climate change, and to recognize fundamental patterns of molecular evolutions. The discovery and description of sulfur-related biochemistry also provides important impulses for biotechnological innovation. In this very active field we plan to pursue the following key aims: 1) Mechanistic characterization of enzymes that mediate oxidative carbon-sulfur transfers. 2) Prospecting the landscape of EGT biosynthesis. 3) Description of a novel class of sulfur metabolites. 4) Characterisation of the catalytic mechanism of the formylglycine generating enzyme.

The goal of this project is to develop a general system for preparative enzyme-catalyzed methylation reactions. Selective methylation of complex molecules can be challenging for synthetic chemistry. Given the exquisite chemo-, regio- and stereoselectivities of enzyme catalysis we believe that biocatalysis presents a powerful alternative for commercial production of pharmaceuticals and fine chemicals. In this project we demonstrate the applicability and commercial viability of a novel enzyme-based technology to preparative methylation reactions.

We retrosynthetically designed a pathway along a completely novel set of new-to-nature metabolites for the synthesis of a high-value-added product currently. The pathway will be implemented using rational design approaches complemented by advanced high throughput screening methods for the reprogramming of the substrate specificities of known enzymes.

Many photophysical and photochemical processes which are relevant for light-to-chemical energy conversion occur on very rapid timescales. Time-resolved UV-Vis absorption spectroscopy has become an indispensable tool in modern photochemistry. Several ongoing Ph. D. theses and postdoctoral research projects in the main applicant's group ask for a transient absorption spectrometer with picosecond time resolution and an appropriate laser source. Among these projects are for example the investigation of photoinduced multi-electron transfer reactions in order to spatially separate multiple electrons from multiple holes, which is of key importance for producing chemical fuels with sunlight as energy input (projects 1 and 2). Similarly, picosecond transient absorption spectrosocopy will permit mechanistic studies of photoinduced proton-coupled electron transfer (PCET) reactions which will greatly further our current fundamental understanding of this important class of reactions (project 3). The activation of small inert molecules such as H 2 O, CO 2 or N 2 will invariably rely on multi-electron, multi-proton chemistry hence the proposed photochemical studies are important in the greater context of solar energy conversion.

Heavy metals, electrophilic toxins and reactive oxygen species are common stressors of cellular live and are the cause of many human health problems such as mental disorder, inflammatory disease and numerous cancers. Plants and microorganisms are vulnerable to the same chemical stressors, but some of these species have acquired remarkable resilience that allows them to strife under very hostile conditions. Elucidation of the underlying mechanisms may provide novel strategies for therapeutic interventions in metal- or redox-induced medical disorders. Sulfur and selenium containing small molecules are key components of cellular defence systems against chemical stress. Microbial resistance to extreme stress often relies on unusual small molecules with remarkable properties. In this project we will investigate the biosynthetic origin and physiological role of a seleno-compound produced by the plant associated bacterium Variovorax paradoxus . This metabolite is also present in humans, but its physiological effects are largely unknown

Oxidative stress causes cancer, cardiovascular, neurodegenerative and infective disease. Much of cellular oxidative stress is mediated, communicated, mitigated or amplified by a complex system of sulfur containing small metabolites or protein-based cysteines. Characterization of key players and reactions in this network is crucial for preventive and therapeutic interventions. I propose a new perspective on sulfur biochemistry. The reactivity of sulfur with the oxidative stressors superoxide, peroxides or hydroxyl radicals is well established, but far less is known about reactions between sulfur and molecular oxygen. I shall demonstrate that this reaction is fundamental to cellular life, and how advances in this field provide new options in medicine, biotechnology and the food industry. Assisted by a team of three PhD students and a postdoctoral researcher I intend to establish this new research field by identification, characterization and engineering of enzymatic activities which catalyse oxidative carbon-sulfur bond formation and cleavage. Specific systems in this study include the biosynthetic enzymes for ergothioneine which is a sulfur containing secondary metabolite with potent activities on cellular functions.

Sulfur containing secondary metabolites are prime modulators of the redox and metal homeostasis in microbial as well as human cells and therefore play important roles in many medical disorders. The identification of novel biothiols and investigation of their biosynthesis physiological functions has gained much interest in the last few years. 3-6 . The enzymology of sulfur incorporation for many of these compounds is not clear and suggesting that much of C-S bond forming biocatalysis is yet to be discovered.

Mehr als 90 % der Biomasse besteht aus dem komplexen und chemisch wertvollen Grundstoff Holz. Um dessen Potential als Brenn-, Bau- und Grundstoff für chemische Synthese zu nutzen, entwickeln wir biokatalytische Methoden zur Modifikation von Lignocellulose. Die globale Photosyntheseleistung produziert jährlich gegen 100 Milliarden Tonnen Lignocellulose aus Kohlenstoffdioxid, Wasser und Sonnenenergie. Pilze und Bakterien mineralisieren beinahe die selbe Menge an Biomasse um daraus Energie und Nährstoffe zu gewinnen. Besonders Pilze vermögen also feste Biomasse effizient in wasserlösliche oder gasförmige Produkte umzusetzen. Die biochemischen Mechanismen dieser Abbauprozesse sind aber zu wenig erforscht, als dass deren industrielle Anwendungen bisher gelungen wären. Zum Beispiel wird Biopulping, also die Gewinnung von Zellulosefasern aus Holz durch Pilze, trotz intensiver Forschung nicht kommerziell angewendet. Molekulares Verständnis der biokatalytischen Zersetzung von Lignin und Lignocellulose durch Pilzenzyme ist eine wichtige Voraussetzung um den Rohstoff Holz angemessener Wertschöpfung zuzuführen. Lignocellulose ist ein fester Stoff und nur dessen Oberfläche ist für enzymatische Transformation zugänglich. Diese Eigenschaft, zusammen mit der chemischen Stabilität der Ligninpolymere macht Lignocellulose ein besonders schwieriges Substrat. Wir fragen: a) wie erkennen lignin-abbauende Enzyme die Oberfläche ihres Substrates? b) Wie verändert sich die Aktivität dieser Enzyme, wenn sie an der Substratoberfläche adsorbieren? c) Können lignin-erkennende Proteindomänen diesen Enzymen zu grösserer Aktivität verhelfen? Um diese Fragen zu beantworten, werden wir verschiedene künstliche Proteine und Proteinkomplexe konstruieren und deren lignin-abbauende Aktivität charakterisieren. In einem nächsten Schritt werden wir prüfen, ob Lignocellulose ist eine wertvolle aber bisher chemisch schwer zugängliche Quelle von organischen Grundstoffen. Die Entwicklung biotechnologischer Methoden zur zielgerichteten Zerlegung oder Modifikation von Holz im industriellen Massstab, würde unserer Gesellschaft eine billige und lokal nachwachsende Ressource erschliessen.

Almost all known aerobic oxidation processes depend on transition metals or small aromatic molecules for O 2 activation. However, several recent reports hint at alternative ways by which enzymes might utilize triplet O 2 to oxidize singlet biomolecules. If true this would allow for novel opportunities in biocatalyst design but it might also suggest that small and large molecules not previously considered redox catalysts might be a source for significant oxidative stress related to aging and infective disease. We propose that a cysteine residue oxidixed to sulfenic acid within an appropriately evolved enzyme active site may serve as a redox catalyst by engaging in one- electron transfers. This proposal integrates thermodynamic considerations and experimental observations on small molecules but clearly departs from traditional enzymology. We identified a bacterial formylglycine-generating enzyme as an ideal model to test this proposal. This enzyme has been structurally characterized but its mechanism remains elusive.