Palladium Nanoparticles from Desulfovibrio alaskensis G20 Catalyze Biocompatible Sonogashira and Biohydrogenation Cascades

Transition-metal nanoparticles produced by living bacteria are emerging as novel catalysts for sustainable synthesis. However, the scope of their catalytic activity and their ability to be integrated within metabolic pathways for the bioproduction of non-natural small molecules has been underexplored. Herein we report that Pd nanoparticles synthesized by the sulfate-reducing bacterium Desulfovibrio alaskensis G20 (DaPdNPs) catalyze the Sonogashira coupling of phenyl acetylenes and aryl iodides, and the subsequent one-pot hydrogenation to bibenzyl derivatives using hydrogen gas generated from d-glucose by engineered Escherichia coli DD-2. The formal hydroarylation reaction is biocompatible, occurs in aqueous media at ambient temperature, and affords products in 70-99% overall yield. This is the first reported microbial nanoparticle to catalyze the Sonogashira reaction and the first demonstration that these biogenic catalysts can be interfaced with the products of engineered metabolism for small molecule synthesis.

Tyramine Derivatives Catalyze the Aldol Dimerization of Butyraldehyde in the Presence of Escherichia coli

Biogenic amine organocatalysts have transformed the field of synthetic organic chemistry. Yet despite their use in synthesis and to label biomolecules in vitro, amine organocatalysis in vivo has received comparatively little attention - despite the potential of such reactions to be interfaced with living cells and to modify cellular metabolites. Herein we report that biogenic amines derived from L-tyrosine catalyze the self-aldol condensation of butanal to 2-ethylhexenal - a key intermediate in the production of the bulk chemical 2-ethylhexanol - in the presence of living Escherichia coli and outperform many amine organocatalysts currently used in synthetic organic chemistry. Furthermore, we demonstrate that cell lysate from E. coli and the prolific amine overproducer Corynebacterium glutamicum ATCC 13032 catalyze this reaction in vitro, demonstrating the potential for microbial metabolism to be used as a source of organocatalysts for biocompatible reactions in cells.

The Bipartisan Future of Synthetic Chemistry and Synthetic Biology

Synthetic biology holds great potential for sustainable chemical synthesis, yet is limited to accessing a relatively small area of chemical space. By interfacing this new technology with the versatility and scope of synthetic chemistry, the best of both worlds can be harnessed to drive a green chemical industry.

Enhancing Biosynthesis and Manipulating Flux in Whole Cells with Abiotic Catalysis

Metabolic engineering uses genetic strategies to drive flux through desired pathways. Recent work with electrochemical, photochemical, and chemocatalytic setups has revealed that these systems can also expand metabolic pathways and manipulate flux in whole cells. Electrochemical systems add or remove electrons from metabolic pathways to direct flux to more- or less-reduced products. Photochemical systems act as synthetic light-harvesting complexes and yield artificial photosynthetic organisms. Biocompatible chemocatalysis increases product scope, streamlines syntheses, and yields single-flask processes to deliver products that would be challenging to synthesize through biosynthetic means alone. Here, we exclusively highlight systems that combine abiotic systems with living whole cells, taking particular note of strategies that enable the merger of these typically disparate systems.

Synthetic Cross-linking of Peptides: Molecular Linchpins for Peptide Cyclization

Peptide-derived drugs constitute a significant fraction of therapeutic agents. In 2013, The global market of peptide therapeutics was ca. $19 billion; this value does not include revenue from insulin derivatives of $28 million. The combined sales of insulin and non-insulin peptide drugs is estimated to exceed $70 billion by 2019. A significant fraction of peptide-derived drugs is composed of an amino acid sequence and additional chemical functionalities that improve biological and pharmacological properties of the drug. In this review, we focus on synthetic cross-linkers that we refer to as "linchpins", which are commonly used to constrain the secondary structure of peptides and equip them with added benefits such as resistance to proteolytic degradation and conformational stability. The latter property leads to an increase in binding potency and increased bioavailability due to increased permeation through biological membranes. Some linchpins can even introduce properties not found in natural peptides such as light-responsiveness. Peptides cyclized by linchpins can be viewed as a sub-class of a larger family of peptide-derived drugs with desired pharmacological performance in vivo. To understand how chemical modifications by linchpins improve drug discovery, this review also briefly summarizes canonical examples of chemical modification used in modern peptide therapeutics.

Firefly Luciferin-Inspired Biocompatible Chemistry for Protein Labeling and In Vivo Imaging

Biocompatible reactions have emerged as versatile tools to build various molecular imaging probes that hold great promise for the detection of biological processes in vitro and/or in vivo. In this Minireview, we describe the recent advances in the development of a firefly luciferin-inspired biocompatible reaction between cyanobenzothiazole (CBT) and cysteine (Cys), and highlight its versatility to label proteins and build multimodality molecular imaging probes. The review starts from the general introduction of biocompatible reactions, which is followed by briefly describing the development of the firefly luciferin-inspired biocompatible chemistry. We then discuss its applications for the specific protein labeling and for the development of multimodality imaging probes (fluorescence, bioluminescence, MRI, PET, photoacoustic, etc.) that enable high sensitivity and spatial resolution imaging of redox environment, furin and caspase-3/7 activity in living cells and mice. Finally, we offer the conclusions and our perspective on the various and potential applications of this reaction. We hope that this review will contribute to the research of biocompatible reactions for their versatile applications in protein labeling and molecular imaging.

Integrating biocompatible chemistry and manipulating cofactor partitioning in metabolically engineered Lactococcus lactis for fermentative production of (3S)-acetoin

Biocompatible chemistry (BC), that is, non-enzymatic chemical reactions compatible with living organisms, is increasingly used in conjunction with metabolically engineered microorganisms for producing compounds that do not usually occur naturally. Here we report production of one such compound, (3S)-acetoin, a valuable precursor for chiral synthesis, using a metabolically engineered Lactococcus lactis strain growing under respiratory conditions with ferric iron serving as a BC component. The strain used has all competing product pathways inactivated, and an appropriate cofactor balance is achieved by fine-tuning the respiratory capacity indirectly via the hemin concentration. We achieve high-level (3S)-acetoin production with a final titer of 66 mM (5.8 g/L) and a high yield (71% of the theoretical maximum). To the best of our knowledge, this is the first report describing production of (3S)-acetoin from sugar by microbial fermentation, and the results obtained confirm the potential that lies with BC for producing useful chemicals. Biotechnol. Bioeng. 2016;113: 2744-2748. © 2016 Wiley Periodicals, Inc.