Direct solar-powered production of value-added chemicals from CO2 and H2O, a process that mimics natural photosynthesis, is of fundamental and practical interest. In natural photosynthesis, CO2 is ...first reduced to common biochemical building blocks using solar energy, which are subsequently used for the synthesis of the complex mixture of molecular products that form biomass. Here we report an artificial photosynthetic scheme that functions via a similar two-step process by developing a biocompatible light-capturing nanowire array that enables a direct interface with microbial systems. As a proof of principle, we demonstrate that a hybrid semiconductor nanowire-bacteria system can reduce CO2 at neutral pH to a wide array of chemical targets, such as fuels, polymers, and complex pharmaceutical precursors, using only solar energy input. The high-surface-area silicon nanowire array harvests light energy to provide reducing equivalents to the anaerobic bacterium, Sporomusa ovata, for the photoelectrochemical production of acetic acid under aerobic conditions (21% O2) with low overpotential (η < 200 mV), high Faradaic efficiency (up to 90%), and long-term stability (up to 200 h). The resulting acetate (∼6 g/L) can be activated to acetyl coenzyme A (acetyl-CoA) by genetically engineered Escherichia coli and used as a building block for a variety of value-added chemicals, such as n-butanol, polyhydroxybutyrate (PHB) polymer, and three different isoprenoid natural products. As such, interfacing biocompatible solid-state nanodevices with living systems provides a starting point for developing a programmable system of chemical synthesis entirely powered by sunlight.
Both natural products and synthetic organofluorines play important roles in the discovery and design of pharmaceuticals. The combination of these two classes of molecules has the potential to be ...useful in the ongoing search for new bioactive compounds but our ability to produce site-selectively fluorinated natural products remains limited by challenges in compatibility between their high structural complexity and current methods for fluorination. Living systems provide an alternative route to chemical fluorination and could enable the production of organofluorine natural products through synthetic biology approaches. While the identification of biogenic organofluorines has been limited, the study of the native organisms and enzymes that utilize these compounds can help to guide efforts to engineer the incorporation of this unusual element into complex pharmacologically active natural products. This review covers recent advances in understanding both natural and engineered production of organofluorine natural products.
Exploring bacterial lignin degradation Brown, Margaret E; Chang, Michelle CY
Current opinion in chemical biology,
April 2014, 2014-Apr, 2014-04-00, 20140401, Letnik:
19
Journal Article
Recenzirano
•Exploring diversity in microbial lignin degradation.•Elucidating lignin metabolism in bacteria.•Discovery of new microbes and microbial consortia that degrade lignin.
Plant biomass represents a ...renewable carbon feedstock that could potentially be used to replace a significant level of petroleum-derived chemicals. One major challenge in its utilization is that the majority of this carbon is trapped in the recalcitrant structural polymers of the plant cell wall. Deconstruction of lignin is a key step in the processing of biomass to useful monomers but remains challenging. Microbial systems can provide molecular information on lignin depolymerization as they have evolved to break lignin down using metalloenzyme-dependent radical pathways. Both fungi and bacteria have been observed to metabolize lignin; however, their differential reactivity with this substrate indicates that they may utilize different chemical strategies for its breakdown. This review will discuss recent advances in studying bacterial lignin degradation as an approach to exploring greater diversity in the environment.
Malaria is a global health problem that threatens 300-500 million people and kills more than one million people annually. Disease control is hampered by the occurrence of multi-drug-resistant strains ...of the malaria parasite Plasmodium falciparum. Synthetic antimalarial drugs and malarial vaccines are currently being developed, but their efficacy against malaria awaits rigorous clinical testing. Artemisinin, a sesquiterpene lactone endoperoxide extracted from Artemisia annua L (family Asteraceae; commonly known as sweet wormwood), is highly effective against multi-drug-resistant Plasmodium spp., but is in short supply and unaffordable to most malaria sufferers. Although total synthesis of artemisinin is difficult and costly, the semi-synthesis of artemisinin or any derivative from microbially sourced artemisinic acid, its immediate precursor, could be a cost-effective, environmentally friendly, high-quality and reliable source of artemisinin. Here we report the engineering of Saccharomyces cerevisiae to produce high titres (up to 100 mg l-1) of artemisinic acid using an engineered mevalonate pathway, amorphadiene synthase, and a novel cytochrome P450 monooxygenase (CYP71AV1) from A. annua that performs a three-step oxidation of amorpha-4,11-diene to artemisinic acid. The synthesized artemisinic acid is transported out and retained on the outside of the engineered yeast, meaning that a simple and inexpensive purification process can be used to obtain the desired product. Although the engineered yeast is already capable of producing artemisinic acid at a significantly higher specific productivity than A. annua, yield optimization and industrial scale-up will be required to raise artemisinic acid production to a level high enough to reduce artemisinin combination therapies to significantly below their current prices.
Natural photosynthesis harnesses solar energy to convert CO₂ and water to value-added chemical products for sustaining life. We present a hybrid bioinorganic approach to solar-to-chemical conversion ...in which sustainable electrical and/or solar input drives production of hydrogen from water splitting using biocompatible inorganic catalysts. The hydrogen is then used by living cells as a source of reducing equivalents for conversion of CO₂ to the value-added chemical product methane. Using platinum or an earth-abundant substitute, α-NiS, as biocompatible hydrogen evolution reaction (HER) electrocatalysts andMethanosarcina barkerias a biocatalyst for CO₂ fixation, we demonstrate robust and efficient electrochemical CO₂ to CH₄ conversion at up to 86% overall Faradaic efficiency for ≥7 d. Introduction of indium phosphide photocathodes and titanium dioxide photoanodes affords a fully solar-driven system for methane generation from water and CO₂, establishing that compatible inorganic and biological components can synergistically couple light-harvesting and catalytic functions for solar-to-chemical conversion.
Plant biomass represents a renewable feedstock that has not yet been fully tapped because of the difficulty in accessing the carbon in its structural biopolymers. Lignin is an especially challenging ...substrate, but select microbes have evolved complex systems of enzymes for its breakdown through a radical-mediated oxidation process. Fungal systems are well-characterized for their ability to depolymerize lignin, but the ability of bacteria to react with this substrate remains elusive. We have therefore focused on elucidating strategies used by lignin-reactive soil bacteria and describing their oxidative enzyme systems. We now report the identification and characterization of an unusual C-type dye-decolorizing peroxidase from Amycolatopsis sp. 75iv2 (DyP2), which belongs to a family of heme peroxidases reported to be involved in bacterial lignin degradation. Biochemical studies indicate that DyP2 has novel function for this family, with versatile and high activity both as a peroxidase and Mn peroxidase (k(cat)/K(M) ≈ 10(5)-10(6) M(-1) s(-1)). It also has a Mn-dependent oxidase mode of action that expands its substrate scope. Crystallographic studies of DyP2 at 2.25 Å resolution show the existence of a Mn binding pocket and support its key role in catalysis.
We present the synthesis, properties, and biological applications of Peroxyfluor-1 (PF1), a new type of optical probe for intracellular imaging of hydrogen peroxide in living biological samples. PF1 ...utilizes a boronate deprotection mechanism to provide unprecedented selectivity and optical dynamic range for detecting H2O2 in aqueous solution over similar reactive oxygen species including superoxide, nitric oxide, tert-butyl hydroperoxide, and hydroxyl radical. We further demonstrate the value of this reagent for biological applications by imaging changes in H2O2 in living mammalian cells.
Organofluorines represent a rapidly expanding proportion of molecules that are used in Pharmaceuticals, diagnostics, agrochemicals, and materials. Despite the prevalence of fluorine in synthetic ...compounds, the known biological scope is limited to a single pathway that produces fluoroacetate. Here, we demonstrate that this pathway can be exploited as a source of fluorinated building blocks for introduction of fluorine into natural-product scaffolds. Specifically, we have constructed pathways involving two polyketide synthase systems, and we show that fluoroacetate can be used to incorporate fluorine into the polyketide backbone in vitro. We further show that fluorine can be inserted site-selectively and introduced into polyketide products in vivo. These results highlight the prospects for the production of complex fluorinated natural products using synthetic biology.
Aldolases are C−C bond forming enzymes that have become prominent tools for sustainable synthesis of complex synthons. However, enzymatic methods of fluorine incorporation into such compounds are ...lacking due to the rarity of fluorine in nature. Recently, the use of fluoropyruvate as a non‐native aldolase substrate has arisen as a solution. Here, we report that the type II HpcH aldolases efficiently catalyze fluoropyruvate addition to diverse aldehydes, with exclusive (3S)‐selectivity at fluorine that is rationalized by DFT calculations on a mechanistic model. We also measure the kinetic parameters of aldol addition and demonstrate engineering of the hydroxyl group stereoselectivity. Our aldolase collection is then employed in the chemoenzymatic synthesis of novel fluoroacids and ester derivatives in high stereopurity (d.r. 80–98 %). The compounds made available by this method serve as precursors to fluorinated analogs of sugars, amino acids, and other valuable chiral building blocks.
Pyruvate aldolases of the type II HpcH family are excellent catalysts for fluoropyruvate addition to aldehydes. The stereoselectivity and kinetic behavior are rationalized, and engineering of hydroxyl stereoselectivity is demonstrated. Downstream reactions allow the synthesis of numerous fluorinated analogs of sugars, amino acids, and other valuable chiral organofluorines.
Fluorine is a critical element for the design of bioactive compounds, driving advances in selective and sustainable fluorination. However, stereogenic tertiary fluorides pose a synthetic challenge ...and are thus present in only a few approved drugs (fluticasone, solithromycin, and sofosbuvir). The aldol reaction of fluorinated donors provides an atom‐economical approach to asymmetric C−F motifs via C−C bond formation. We report that the type II pyruvate aldolase HpcH and engineered variants perform addition of β‐fluoro‐α‐ketoacids (including fluoropyruvate, β‐fluoro‐α‐ketobutyrate, and β‐fluoro‐α‐ketovalerate) to diverse aldehydes. The reactivity of HpcH towards these fluoro‐donors grants access to enantiopure secondary or tertiary fluorides. In addition to representing the first synthesis of tertiary fluorides via biocatalytic carboligation, the afforded products could improve the diversity of fluorinated building blocks and enable the synthesis of fluorinated drug analogs.
Biocatalytic asymmetric synthesis of secondary and tertiary fluorides is performed by the pyruvate aldolase HpcH and its engineered variants, utilizing β‐fluoro‐α‐ketoacids as non‐native donor substrates. Rationalization of beneficial mutations and optimization of reaction conditions allowed for the chemoenzymatic preparation of fluorinated synthons with relevance to bioactive natural products and pharmaceuticals.
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