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The B cofactors instill a natural curiosity regarding the primordial selection and evolution of their corrin ligand. Surprisingly, this important natural macrocycle has evaded molecular scrutiny, and its specific role in predisposing the incarcerated cobalt ion for organometallic catalysis has remained obscure. Herein, we report the biosynthesis of the cobalt-free B corrin moiety, hydrogenobyric acid (Hby), a compound crafted through pathway redesign. Detailed insights from single-crystal X-ray and solution structures of Hby have revealed a distorted helical cavity, redefining the pattern for binding cobalt ions. Consequently, the corrin ligand coordinates cobalt ions in desymmetrized "entatic" states, thereby promoting the activation of B -cofactors for their challenging chemical transitions. The availability of Hby also provides a route to the synthesis of transition metal analogues of B .
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http://dx.doi.org/10.1002/anie.201904713 | DOI Listing |
Eur Biophys J
June 2025
Institute of Biophysics, National Research Council, Palermo, Italy.
Vitamin B12 (cobalamin, Cbl) is a coordination compound of the cobalt, located at the center of a corrin ring composed of four pyrrolic-like groups. The cobalt ion can be bound to a variety of upper axial ligands, which vary among different cobalamin forms, including hydroxocobalamin (OHCbl), cyanocobalamin (CNCbl), methylcobalamin (MeCbl), and adenosylcobalamin (AdoCbl). MeCbl and AdoCbl are considered the biologically active forms, serving as cofactors in the metabolism of methylmalonic acid (MMA) and homocysteine (HCY).
View Article and Find Full Text PDFChem Commun (Camb)
July 2025
Institute of Organic Chemistry, University of Innsbruck, 6020 Innsbruck, Austria.
The d-Cu(II)-corrin cupribyrate (Cuby) was synthesized in 93% crystalline yield by rapid chelation of Cu-ions by the metal-free corrin-ligand of vitamin B. Single crystals of the EPR-active Cuby allowed for the first X-ray structure determination of a Cu-corrin. SCF-calculations provided insights complementary to the experimental data of Cuby and indicated an out-of-plane displacement of the reduced d-Cu(I)-ion, consistent with the observed reductive activation of Cuby towards loss of its Cu-center.
View Article and Find Full Text PDFChem Commun (Camb)
February 2025
Institute of Organic Chemistry, University of Innsbruck, A-6020 Innsbruck, Austria.
The photoexcited state of the corrin-ligand of vitamin B is an old puzzle. We show here that the metal-free corrin-ligand emits dual fluorescence in its singlet excited state. As a specific consequence of the asymmetry of the natural corrin-ligand, its strongly emitting singlet excited state exists as a pair of isomers that interconvert rapidly in an unprecedented H/D-Isotope sensitive way in competition with their fluorescent decay.
View Article and Find Full Text PDFFEBS J
February 2025
Department of Functional and Evolutionary Ecology, University of Vienna, Austria.
Corrinoids are cobalt-containing tetrapyrroles. They include adenosylcobalamin (vitamin B) and cobamides that function as cofactors and coenzymes for methyl transfer, radical-dependent and redox reactions. Though cobamides are the most complex cofactors in nature, they are essential in the acetyl-CoA pathway, thought to be the most ancient CO-fixation pathway, where they perform a pterin-to-cobalt-to-nickel methyl transfer reaction catalyzed by the corrinoid iron-sulphur protein (CoFeS).
View Article and Find Full Text PDFFront Chem
September 2024
Department of Organic Chemistry, Arrhenius Laboratory Stockholm University, Stockholm, Sweden.