Investigations on the Biosynthesis of the 5,6‐Dimethylbenzimidazole Moiety of Vitamin B<sub>12</sub>

Renz, Paul

doi:10.1002/9783527612192.ch06

Cited by 2 publications

(1 citation statement)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…FMN (but not FAD) also possesses an important biological function in being the biosynthetic precursor of the dimethylbenzimidazol part of coenzyme B 12 (63,366,367). Conversion of FMN to dimethylbenzimidazol involves a unique transformation reaction with no precedent in chemistry, which includes retro-aldol condensation sandwiched between two 2-electron oxidations (154,519).…”

Section: Biological Role Of Flavinsmentioning

confidence: 99%

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Abbas

Sibirny

2011

Microbiol Mol Biol Rev

316

272

View full text Add to dashboard Cite

SUMMARY Riboflavin [7,8-dimethyl-10-(1′- d -ribityl)isoalloxazine, vitamin B 2 ] is an obligatory component of human and animal diets, as it serves as the precursor of flavin coenzymes, flavin mononucleotide, and flavin adenine dinucleotide, which are involved in oxidative metabolism and other processes. Commercially produced riboflavin is used in agriculture, medicine, and the food industry. Riboflavin synthesis starts from GTP and ribulose-5-phosphate and proceeds through pyrimidine and pteridine intermediates. Flavin nucleotides are synthesized in two consecutive reactions from riboflavin. Some microorganisms and all animal cells are capable of riboflavin uptake, whereas many microorganisms have distinct systems for riboflavin excretion to the medium. Regulation of riboflavin synthesis in bacteria occurs by repression at the transcriptional level by flavin mononucleotide, which binds to nascent noncoding mRNA and blocks further transcription (named the riboswitch). In flavinogenic molds, riboflavin overproduction starts at the stationary phase and is accompanied by derepression of enzymes involved in riboflavin synthesis, sporulation, and mycelial lysis. In flavinogenic yeasts, transcriptional repression of riboflavin synthesis is exerted by iron ions and not by flavins. The putative transcription factor encoded by SEF1 is somehow involved in this regulation. Most commercial riboflavin is currently produced or was produced earlier by microbial synthesis using special selected strains of Bacillus subtilis , Ashbya gossypii , and Candida famata . Whereas earlier RF overproducers were isolated by classical selection, current producers of riboflavin and flavin nucleotides have been developed using modern approaches of metabolic engineering that involve overexpression of structural and regulatory genes of the RF biosynthetic pathway as well as genes involved in the overproduction of the purine precursor of riboflavin, GTP.

show abstract

Section: Biological Role Of Flavinsmentioning

confidence: 99%

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Abbas

Sibirny

2011

Microbiol Mol Biol Rev

316

272

View full text Add to dashboard Cite

show abstract

Native Corrinoids fromClostridium cochleariumAre Adeninylcobamides: Spectroscopic Analysis and Identification of Pseudovitamin B₁₂and Factor A

et al. 2000

View full text Add to dashboard Cite

The corrinoids from the obligate anaerobe Clostridium cochlearium were extracted as a mixture of Co ␤ -cyano derivatives. From 50 g of frozen cells, approximately 2 mg (1.5 mol) of B 12 derivatives was obtained as a crystalline sample. Analysis of the corrinoid sample of C. cochlearium by a combination of high-pressure liquid chromatography and UV-Vis absorbance spectroscopy revealed the presence of three cyano corrinoids in a ratio of about 3:1:1. The spectroscopic data acquired for the sample indicated the main components to be pseudovitamin B 12 (Co ␤ -cyano-7؆-adeninylcobamide) (60%) and factor A (Co ␤ -cyano-7؆-[2-methyl]adeninylcobamide) (20%). Authentic pseudovitamin B 12 was prepared by guided biosynthesis from cobinamide and adenine. Both pseudovitamin B 12 and its homologue, factor A, were subjected to complete spectroscopic analysis by UV-Vis, circular dichroism, mass spectrometry, and by one-and two-dimensional 1 H, 13 C-, and 15 N nuclear magnetic resonance (NMR) spectroscopy. The third component was indicated by the mass spectra to be an isomer of factor A and is likely (according to NMR) to be 7؆-[N 6 -methyl]-adeninylcobamide, a previously unknown corrinoid. C. cochlearium thus biosynthesizes as its native "complete" B 12 cofactors the 7؆-adeninylcobamides and two homologous corrinoids, in which the nucleotide base is a methylated adenine.

show abstract

Investigations on the Biosynthesis of the 5,6‐Dimethylbenzimidazole Moiety of Vitamin B₁₂

Cited by 2 publications

References 44 publications

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Native Corrinoids fromClostridium cochleariumAre Adeninylcobamides: Spectroscopic Analysis and Identification of Pseudovitamin B₁₂and Factor A

Contact Info

Product

Resources

About

Investigations on the Biosynthesis of the 5,6‐Dimethylbenzimidazole Moiety of Vitamin B12

Cited by 2 publications

References 44 publications

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Native Corrinoids fromClostridium cochleariumAre Adeninylcobamides: Spectroscopic Analysis and Identification of Pseudovitamin B12and Factor A

Contact Info

Product

Resources

About

Investigations on the Biosynthesis of the 5,6‐Dimethylbenzimidazole Moiety of Vitamin B₁₂

Native Corrinoids fromClostridium cochleariumAre Adeninylcobamides: Spectroscopic Analysis and Identification of Pseudovitamin B₁₂and Factor A