Dataset Information

Mild olefin formation via bio-inspired vitamin B₁₂ photocatalysis.

ABSTRACT: Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B₁₂-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B₁₂-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B₁₂ to be a powerful platform for developing mild olefin-forming reactions.

SUBMITTER: Bam R

PROVIDER: S-EPMC8179286 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Mild olefin formation via bio-inspired vitamin B12 photocatalysis.

Bam Radha R Pollatos Alexandros S AS Moser Austin J AJ West Julian G JG

Chemical science 20201208 5

Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond ...[more]

PMID: 34163933

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Project description:Vitamin B12 is synthesized only by certain bacteria and archaeon, but not by plants. The synthesized vitamin B12 is transferred and accumulates in animal tissues, which can occur in certain plant and mushroom species through microbial interaction. In particular, the meat and milk of herbivorous ruminant animals (e.g. cattle and sheep) are good sources of vitamin B12 for humans. Ruminants acquire vitamin B12, which is considered an essential nutrient, through a symbiotic relationship with the bacteria present in their stomachs. In aquatic environments, most phytoplankton acquire vitamin B12 through a symbiotic relationship with bacteria, and they become food for larval fish and bivalves. Edible plants and mushrooms rarely contain a considerable amount of vitamin B12, mainly due to concomitant bacteria in soil and/or their aerial surfaces. Thus, humans acquire vitamin B12 formed by microbial interaction via mainly ruminants and fish (or shellfish) as food sources. In this review, up-to-date information on vitamin B12 sources and bioavailability are also discussed. Impact statement To prevent vitamin B12 (B12) deﬁciency in high-risk populations such as vegetarians and elderly subjects, it is necessary to identify foods that contain high levels of B12. B12 is synthesized by only certain bacteria and archaeon, but not by plants or animals. The synthesized B12 is transferred and accumulated in animal tissues, even in certain plant tissues via microbial interaction. Meats and milks of herbivorous ruminant animals are good sources of B12 for humans. Ruminants acquire the essential B12 through a symbiotic relationship with bacteria inside the body. Thus, we also depend on B12-producing bacteria located in ruminant stomachs. While edible plants and mushrooms rarely contain a considerable amount of B12, mainly due to concomitant bacteria in soil and/or their aerial surfaces. In this mini-review, we described up-to-date information on B12 sources and bioavailability with reference to the interaction of microbes as B12-producers.

Project description:Vitamin B12 (cobalamin, herein B12) is a key cofactor for most organisms being involved in essential metabolic processes. In microbial communities, B12 is often scarce, largely because only few prokaryotes can synthesize B12 de novo and are thus considered B12-prototrophs. B12-auxotrophy is mostly manifested by the absence of the B12-independent methionine synthase, MetE. Here, we focus on bacteria that we classified as facultative B12 consumers as they encode both B12-independent and -dependent (MetH) methionine synthases yet largely cannot synthesize B12 de novo. The genus Vibrio belongs to this group, and our work shows that upon B12 supply growth of Vibrio campbellii is accelerated and autoinducer-2 (AI-2) concentrations are enhanced. We speculate that methionine synthesis efficiency, dependent on B12 availability, is linked to AI-2 synthesis. The precursor for AI-2 synthesis is S-adenosyl-L-homocysteine (SAH), which in turn requires methionine as a precursor. In almost all Vibrio species studied, btuF (B12-binding protein), which is required for B12 uptake, and cobD (Adenosylcobinamide-phosphate synthase), which enables remodeling of B12-like compounds, are encoded on the same operon as pfs (or mtnN, Adenosylhomocysteine nucleosidase), the first enzyme in the two-step AI-2 synthesis reaction. Transcriptomic analyses show that virulence factors, such as toxin synthesis, fimbriae formation, and activation of the type-6 secretion system, which have been shown to be regulated by quorum sensing via AI-2, are significantly upregulated in V. campbellii when B12 is available. Our results demonstrate that V. campbellii is a facultative B12 consumer and indicate that B12 availability affects AI-2 levels and thus potentially virulence factor regulation.IMPORTANCEMetabolites play a key role in microbial metabolism and communication. While vitamin B12 is an essential cofactor for important enzymatic reactions, autoinducer-2 mediates interspecies signaling and can regulate the expression of genes that are crucial for virulence and survival. In our study, we hypothesize and present findings how these two important metabolites are linked in Vibrio species. Vibrio campbellii grows without B12 but at an accelerated rate when B12 is present, and we detect higher AI-2 values in cultures with B12 amendment. Transcriptome analyses show how vitamin B12 availability significantly upregulates gene expression of virulence factors such as toxin synthesis, fimbrial formation, and activation of the type-6 secretion system in V. campbellii.

Dataset Information

Mild olefin formation via bio-inspired vitamin B₁₂ photocatalysis.

Publications

Mild olefin formation <i>via</i> bio-inspired vitamin B<sub>12</sub> photocatalysis.

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