Vitamin B12 (Cobalamin) Biosynthesis in the Purple Bacteria

2009 ◽  
pp. 81-95 ◽  
Author(s):  
Martin J. Warren ◽  
Evelyne Deery
Keyword(s):  
Vitamin B12 ◽  
Purple Bacteria ◽  
Cobalamin Biosynthesis

Aerobic synthesis of vitamin B12: ring contraction and cobalt chelation

2005 ◽  
Vol 33 (4) ◽  
pp. 815-819 ◽  
Author(s):  
D. Heldt ◽  
A.D. Lawrence ◽  
M. Lindenmeyer ◽  
E. Deery ◽  
P. Heathcote ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Metal Ion ◽  
Biosynthetic Pathway ◽  
Rhodobacter Capsulatus ◽  
Chlorophyll Synthesis ◽  
Subsequent Reduction ◽  
Ring Contraction ◽  
Contraction Process ◽  
Cobalamin Biosynthesis ◽  
Haem Iron

The aerobic biosynthetic pathway for vitamin B12 (cobalamin) biosynthesis is reviewed. Particular attention is focused on the ring contraction process, whereby an integral carbon atom of the tetrapyrrole-derived macrocycle is removed. Previous work had established that this chemically demanding step is facilitated by the action of a mono-oxygenase called CobG, which generates a hydroxy lactone intermediate. This mono-oxygenase contains both a non-haem iron and an Fe-S centre, but little information is known about its mechanism. Recent work has established that in bacteria such as Rhodobacter capsulatus, CobG is substituted by an isofunctional protein called CobZ. This protein has been shown to contain flavin, haem and Fe-S centres. A mechanism is proposed to explain the function of CobZ. Another interesting aspect of the aerobic cobalamin biosynthetic pathway is cobalt insertion, which displays some similarity to the process of magnesium chelation in chlorophyll synthesis. The genetic requirements of cobalt chelation and the subsequent reduction of the metal ion are discussed.

scholarly journals Metagenomic- and Cultivation-Based Exploration of Anaerobic Chloroform Biotransformation in Hypersaline Sediments as Natural Source of Chloromethanes

2020 ◽  
Vol 8 (5) ◽  
pp. 665
Author(s):  
Peng Peng ◽  
Yue Lu ◽  
Tom N.P. Bosma ◽  
Ivonne Nijenhuis ◽  
Bart Nijsse ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Reductive Dechlorination ◽  
Electron Donors ◽  
Natural Source ◽  
Hypersaline Lake ◽  
Reductive Dehalogenase ◽  
Enrichment Cultures ◽  
Cobalamin Biosynthesis ◽  
Abiotic Control ◽  
Hypersaline Sediments

Chloroform (CF) is an environmental contaminant that can be naturally formed in various environments ranging from forest soils to salt lakes. Here we investigated CF removal potential in sediments obtained from hypersaline lakes in Western Australia. Reductive dechlorination of CF to dichloromethane (DCM) was observed in enrichment cultures derived from sediments of Lake Strawbridge, which has been reported as a natural source of CF. No CF removal was observed in abiotic control cultures without artificial electron donors, indicating biotic CF dechlorination in the enrichment cultures. Increasing vitamin B12 concentration from 0.04 to 4 µM in enrichment cultures enhanced CF removal and reduced DCM formation. In cultures amended with 4 µM vitamin B12 and 13C labelled CF, formation of 13CO2 was detected. Known organohalide-respiring bacteria and reductive dehalogenase genes were neither detected using quantitative PCR nor metagenomic analysis of the enrichment cultures. Rather, members of the order Clostridiales, known to co-metabolically transform CF to DCM and CO2, were detected. Accordingly, metagenome-assembled genomes of Clostridiales encoded enzymatic repertoires for the Wood-Ljungdahl pathway and cobalamin biosynthesis, which are known to be involved in fortuitous and nonspecific CF transformation. This study indicates that hypersaline lake microbiomes may act as a filter to reduce CF emission to the atmosphere.

scholarly journals Microbial and Genetic Resources for Cobalamin (Vitamin B12) Biosynthesis: From Ecosystems to Industrial Biotechnology

2021 ◽  
Vol 22 (9) ◽  
pp. 4522
Author(s):  
Larissa Balabanova ◽  
Liudmila Averianova ◽  
Maksim Marchenok ◽  
Oksana Son ◽  
Liudmila Tekutyeva
Keyword(s):  
Vitamin B12 ◽  
Genetic Resources ◽  
Positive Impact ◽  
Metagenomic Data ◽  
Metabolic Reconstruction ◽  
Industrial Biotechnology ◽  
Natural Ecosystems ◽  
Pseudomonas Denitrificans ◽  
Cobalamin Biosynthesis ◽  
Industrial Strains

Many microbial producers of coenzyme B12 family cofactors together with their metabolically interdependent pathways are comprehensively studied and successfully used both in natural ecosystems dominated by auxotrophs, including bacteria and mammals, and in the safe industrial production of vitamin B12. Metabolic reconstruction for genomic and metagenomic data and functional genomics continue to mine the microbial and genetic resources for biosynthesis of the vital vitamin B12. Availability of metabolic engineering techniques and usage of affordable and renewable sources allowed improving bioprocess of vitamins, providing a positive impact on both economics and environment. The commercial production of vitamin B12 is mainly achieved through the use of the two major industrial strains, Propionobacterium shermanii and Pseudomonas denitrificans, that involves about 30 enzymatic steps in the biosynthesis of cobalamin and completely replaces chemical synthesis. However, there are still unresolved issues in cobalamin biosynthesis that need to be elucidated for future bioprocess improvements. In the present work, we review the current state of development and challenges for cobalamin (vitamin B12) biosynthesis, describing the major and novel prospective strains, and the studies of environmental factors and genetic tools effecting on the fermentation process are reported.

Vitamin B12 Content of Liver and Serum in Malignant Neoplasia

1962 ◽  
Vol 42 (4) ◽  
pp. 414-418 ◽  
Author(s):  
Robert S. Nelson ◽  
Vasant M. Doctor
Keyword(s):  
Vitamin B12 ◽  
Malignant Neoplasia

55: The Risk of Vitamin B12 Deficiency is Low after Ileal Orthotopic Bladder Substitution

2004 ◽  
Vol 171 (4S) ◽  
pp. 15-15
Author(s):  
Urs E. Studer ◽  
Richard Aebischer ◽  
Katharina Ochsner ◽  
Werner W. Hochreiter
Keyword(s):  
Vitamin B12 ◽  
Vitamin B12 Deficiency ◽  
B12 Deficiency ◽  
Bladder Substitution

Switching to Oral Vitamin B12 Replacement

2006 ◽  
Vol 39 (18) ◽  
pp. 30
Author(s):  
JON O. EBBERT ◽  
ERIC G. TANGALOS
Keyword(s):  
Vitamin B12 ◽  
Oral Vitamin
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