B<sub>12</sub>‐Coenzymes, the Central Theme

Kräutler, Bernhard

doi:10.1002/9783527612192.ch01

Cited by 4 publications

(5 citation statements)

References 97 publications

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“…This nomenclature rule is illustrated in Figure 1 and follows the one proposed by Sharpless for denoting the two directions of attack of an epoxidation reagent to a planar olefin (Kolb et al 1994). Furthermore, it complies with the nomenclature in use for Fe and Co tetrapyrrloes such as corrins and Vitamin B 12 derivatives, which have the a-ligand of the cobalt atom (usually adenosine) below the tetrapyrrolic plane (Kra¨utler 1998). We would thus like to extend this nomenclature also for other metal tetrapyrroles, which can be five-or sixcoordinated.…”

Section: Introduction and A Note On Nomenclaturementioning

confidence: 95%

Relevance of the Diastereotopic Ligation of Magnesium Atoms of Chlorophylls in the Major Light-harvesting Complex II (LHC II) of Green Plants

Balaban¹

2005

Photosynth Res

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The recent high-resolution crystal structure of LHC II [Liu et al. (2004) Nature 428: 287-292] makes possible an unprecedented insight into the stereochemical features of how chlorophylls (Chl)s are bound. The diastereotopic ligation generates four structurally different pigment types, two Chl a and two Chl b, which are distinguished not only by the groups in the 7-position (methyl in Chl a and formyl in Chl b) but also by the face of the tetrapyrrole to which the fifth magnesium ligand is bound. Within a LHC II monomer, out of the eight Chl a six have a 'normal' alpha-coordination and two are beta-coordinated while out of the six Chl b only one has the 'special' beta-coordination. In Photosystem I where a more meaningful statistical analysis could be made, out of 96 Chl a only 14 are beta-coordinated, again indicating a preference for the 'normal' alpha-coordination [Balaban et al. (2002) Biochim Biophys Acta Bioenerget 1556: 197-207; Oba and Tamiaki (2002a) Photosynth Res 74: 1-10]. Astonishingly, all the special beta-Chls are part of the stromal ring of Chls within the LHC II trimers and occupy key positions for the excitation energy transfer. Sequential energy traps are engineered with one hetero- and three homo-dimers. A careful pairing of carotenoids with the special beta-Chls, which could quench their triplet states efficiently, implies a functional relevance of this diastereotopic ligation.

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Section: Introduction and A Note On Nomenclaturementioning

confidence: 95%

Relevance of the Diastereotopic Ligation of Magnesium Atoms of Chlorophylls in the Major Light-harvesting Complex II (LHC II) of Green Plants

Balaban¹

2005

Photosynth Res

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“…CNCbl is essential for the survival of all living organisms playing a key role in the hematopoiesis, neural metabolism, DNA and RNA production, and carbohydrate, fat, and protein metabolism. 10,11 More than 10 years ago, Alberto and co-workers proposed the idea to use CNCbl as a carrier of CP; 12−14 it was shown that CNCbl can act as a ligand for CP by formation of a cyanide bridged species between the β-axial ligand of CNCbl and the square-planar platinum complex. 12 The CNCbl–CP conjugate retains a labile chloride ligand that can be exchanged within cells, allowing the conjugate to behave in a comparable way to CP.…”

Section: Introductionmentioning

confidence: 99%

Structural Elucidation of Cisplatin and Hydrated cis-Diammineplatinum(II) Complex Conjugated with Cyanocobalamin by Liquid Chromatography with Electrospray Ionization–Mass Spectrometry and Multistage Mass Spectrometry

et al. 2018

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Pt(II)-based derivatives bearing a cyanocobalamin (CNCbl) unit were synthesized in aqueous solutions, and the reaction mixtures were examined by reversed-phase liquid chromatography with electrospray ionization and linear ion trap mass spectrometry (MS). Isotopic pattern analysis, multistage mass-spectra (MS/MS and MS 3 ) interpretation, and differential isotopic labeling were used to establish the chemical composition and to suggest the chemical structures of reaction products. When cisplatin ( cis -[PtCl 2 (NH 3 ) 2 ]) was used as a Pt(II) drug derivative, a coordination bond between diamminemonochloroplatinum(II) and the cyano group of CNCbl, in turn linked covalently to the vitamin Co(III) ion, occurred. The resulting conjugate with a Co III –CN–Pt II bridge was MS detected as a doubly positive charged ion with the prevailing isotopologue at m / z 810.26 (empirical formula [C 63 H 95 ClCo III N 16 O 14 PPt] 2+ ). Likewise, a peak signal centered at m / z 811.26 was observed when 15 N-labeled cisplatin cis -[PtCl 2 ( 15 NH 3 ) 2 ] was used as Pt(II) complex, thus confirming the presence of both the cisplatin amino groups in the conjugate. A bifunctional conjugate was obtained between CNCbl and the cis -diamminediaquaplatinum(II), that is, cis -[Pt(NH 3 ) 2 (H 2 O) 2 ] 2+ ; in this case, the planar coordination complex of Pt(II) was also involved in a covalent bond with the oxygen atom of one of the CNCbl amide moieties. The peak signal detected at m / z 792.26 (empirical formula [C 63 H 94 Co III N 16 O 14 PPt] 2+ ) changed to m / z 793.26 when the labeled cis -[Pt( 15 NH 3 ) 2 (H 2 O) 2 ] 2+ complex was adopted for conjugation. Comparison between MS/MS spectra allowed an extended structural characterization of both conjugates, as such or 15 N-labeled. Two-dimensional heteronuclear ( 1 H– 15 N) single quantum correlation NMR spectroscopy, applied to 15 ...

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“…4 Otherwise, corrinoids are prone to reduction and produce a brown-yellow Co(II) or green Co(I) form, depending on the strength of the reducing agents, 11 yet these forms are readily oxidized by atmospheric oxygen with restoration of the "normal" red color. 4,12,13 Three acetamide and four propionamide side chains (indexed as a, b, c, d, e, f, and g) project to either the "upper" or the "lower" face of the corrin ring (see Figure 1A). 3 They provide specific hydrogen bonding interactions between the corrinoid and an enzyme or a Cbl-transporting protein (see below for further discussion).…”

mentioning

confidence: 99%

“…4 The transition to a "base-off" form is also facilitated by low pH values, due to protonation of DMB. Substitution of DMB with adenine, as seen in pseudocoenzyme B 12 , also shifts the equilibrium to the base-off form. 6 In some enzymes, the base-off form of Cbl cofactors is required for catalysis, 7,8 whereas the proteins of Cbl transport preferentially bind the chemically more stable base-on forms.…”

mentioning

confidence: 99%

A Blue Corrinoid from Partial Degradation of Vitamin B₁₂in Aqueous Bicarbonate: Spectra, Structure, and Interaction with Proteins of B₁₂Transport

et al. 2011

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Cobalamin (Cbl) is a complex cofactor produced only by bacteria but used by all animals and humans. Cyanocobalamin (vitamin B(12), CNCbl) is one commonly isolated form of cobalamin. B(12) belongs to a large group of corrinoids, which are characterized by a distinct red color conferred by the system of conjugated double bonds of the corrin ring retaining a Co(III) ion. A unique blue Cbl derivative was produced by hydrolysis of CNCbl in a weakly alkaline aqueous solution of bicarbonate. This corrinoid was purified and isolated as dark blue crystals. Its spectroscopic analysis and X-ray crystallography revealed B-ring opening with formation of 7,8-seco-cyanocobalamin (7,8-sCNCbl). The unprecedented structural change was caused by cleavage of the peripheral C-C bond between saturated carbons 7 and 8 of the corrin macrocycle accompanied by formation of a C═C bond at C7 and a carbonyl group at C8. Additionally, the C-amide was hydrolyzed to a carboxylic acid. The extended conjugation of the π-system caused a considerable red shift of the absorbance spectrum. Formation and degradation of 7,8-sCNCbl were analyzed qualitatively. Its interaction with the proteins of mammalian Cbl transport revealed both a slow binding kinetics and a low overall affinity. The binding data were compared to those of other monocarboxylic derivatives and agreed with the earlier proposed scheme for two-step ligand recognition. The obtained results are consistent with the structural models of 7,8-sCNCbl and the transport proteins intrinsic factor and transcobalamin. Potential applications of the novel derivative for drug conjugation are discussed.

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B₁₂‐Coenzymes, the Central Theme

Cited by 4 publications

References 97 publications

Relevance of the Diastereotopic Ligation of Magnesium Atoms of Chlorophylls in the Major Light-harvesting Complex II (LHC II) of Green Plants

Relevance of the Diastereotopic Ligation of Magnesium Atoms of Chlorophylls in the Major Light-harvesting Complex II (LHC II) of Green Plants

Structural Elucidation of Cisplatin and Hydrated cis-Diammineplatinum(II) Complex Conjugated with Cyanocobalamin by Liquid Chromatography with Electrospray Ionization–Mass Spectrometry and Multistage Mass Spectrometry

A Blue Corrinoid from Partial Degradation of Vitamin B₁₂in Aqueous Bicarbonate: Spectra, Structure, and Interaction with Proteins of B₁₂Transport

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B12‐Coenzymes, the Central Theme

Cited by 4 publications

References 97 publications

Relevance of the Diastereotopic Ligation of Magnesium Atoms of Chlorophylls in the Major Light-harvesting Complex II (LHC II) of Green Plants

Relevance of the Diastereotopic Ligation of Magnesium Atoms of Chlorophylls in the Major Light-harvesting Complex II (LHC II) of Green Plants

Structural Elucidation of Cisplatin and Hydrated cis-Diammineplatinum(II) Complex Conjugated with Cyanocobalamin by Liquid Chromatography with Electrospray Ionization–Mass Spectrometry and Multistage Mass Spectrometry

A Blue Corrinoid from Partial Degradation of Vitamin B12in Aqueous Bicarbonate: Spectra, Structure, and Interaction with Proteins of B12Transport

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B₁₂‐Coenzymes, the Central Theme

A Blue Corrinoid from Partial Degradation of Vitamin B₁₂in Aqueous Bicarbonate: Spectra, Structure, and Interaction with Proteins of B₁₂Transport