How corrinoids are synthesized without oxygen: nature's first pathway to vitamin B12

Santander, Patricio J.; Roessner, Charles A.; Stolowich, Neal J.; Holderman, Marc T.; Scott, A. Ian

doi:10.1016/s1074-5521(97)90221-0

Cited by 54 publications

(33 citation statements)

References 20 publications

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“…Second, it is clear that Halobacterium sp. strain NRC-1 synthesizes cobamides de novo under aerobic conditions, a fact that is somewhat surprising because the cobamide biosynthetic genes of this archaeon are homologous to those found in S. enterica, a bacterium known to use the anaerobic pathway of de novo corrin ring biosynthesis (27). How Halobacterium sp.…”

Section: Resultsmentioning

confidence: 99%

ThecobYGene of the ArchaeonHalobacteriumsp. Strain NRC-1 Is Required for De Novo Cobamide Synthesis

Woodson

Peck²,

Krebs

et al. 2003

J Bacteriol

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Genetic and nutritional analyses of mutants of the extremely halophilic archaeon Halobacterium sp. strain NRC-1 showed that open reading frame (ORF) Vng1581C encodes a protein with nucleoside triphosphate: adenosylcobinamide-phosphate nucleotidyltransferase enzyme activity. This activity was previously associated with the cobY gene of the methanogenic archaeon Methanobacterium thermoautotrophicum strain ⌬H, but no evidence was obtained to demonstrate the direct involvement of this protein in cobamide biosynthesis in archaea. Computer analysis of the Halobacterium sp. strain NRC-1 ORF Vng1581C gene and the cobY gene of M. thermoautotrophicum strain ⌬H showed the primary amino acid sequence of the proteins encoded by these two genes to be 35% identical and 48% similar. A strain of Halobacterium sp. strain NRC-1 carrying a null allele of the cobY gene was auxotrophic for cobinamide-GDP, a known intermediate of the late steps of cobamide biosynthesis. The auxotrophic requirement for cobinamide-GDP was corrected when a wild-type allele of cobY was introduced into the mutant strain, demonstrating that the lack of cobY function was solely responsible for the observed block in cobamide biosynthesis in this archaeon. The data also show that Halobacterium sp. strain NRC-1 possesses a high-affinity transport system for corrinoids and that this archaeon can synthesize cobamides de novo under aerobic growth conditions. To the best of our knowledge this is the first genetic and nutritional analysis of cobalamin biosynthetic mutants in archaea.

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Section: Resultsmentioning

confidence: 99%

ThecobYGene of the ArchaeonHalobacteriumsp. Strain NRC-1 Is Required for De Novo Cobamide Synthesis

Woodson

Peck²,

Krebs

et al. 2003

J Bacteriol

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“…This major biosynthetic pathway has mostly been studied in bacterial systems, with the majority of the work being focused on the anaerobic biosynthesis of the corrin ring in Salmonella enterica (11,27), Propionibacterium freundenreichii subsp. shermanii (29), and Bacillus megaterium (6,23,24) and on aerobic biosynthesis of the corrin ring in Pseudomonas denitrificans (4). This large body of work has given considerable insight into the details of cobamide biosynthesis and has set the basis for comparisons with other organisms (26,38).…”

mentioning

confidence: 99%

A New Pathway for Salvaging the CoenzymeB₁₂Precursor Cobinamide in Archaea RequiresCobinamide-Phosphate Synthase (CbiB) EnzymeActivity

2003

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The ability of archaea to salvage cobinamide has been under question because archaeal genomes lack orthologs to the bacterial nucleoside triphosphate:5-deoxycobinamide kinase enzyme (cobU in Salmonella enterica). The latter activity is required for cobinamide salvaging in bacteria. This paper reports evidence that archaea salvage cobinamide from the environment by using a pathway different from the one used by bacteria. These studies demanded the functional characterization of two genes whose putative function had been annotated based solely on their homology to the bacterial genes encoding adenosylcobyric acid and adenosylcobinamide-phosphate synthases (cbiP and cbiB, respectively) of S. enterica. A cbiP mutant strain of the archaeon Halobacterium sp. strain NRC-1 was auxotrophic for adenosylcobyric acid, a known intermediate of the de novo cobamide biosynthesis pathway, but efficiently salvaged cobinamide from the environment, suggesting the existence of a salvaging pathway in this archaeon. A cbiB mutant strain of Halobacterium was auxotrophic for adenosylcobinamide-GDP, a known de novo intermediate, and did not salvage cobinamide. The results of the nutritional analyses of the cbiP and cbiB mutants suggested that the entry point for cobinamide salvaging is adenosylcobyric acid. The data are consistent with a salvaging pathway for cobinamide in which an amidohydrolase enzyme cleaves off the aminopropanol moiety of adenosylcobinamide to yield adenosylcobyric acid, which is converted by the adenosylcobinamide-phosphate synthase enzyme to adenosylcobinamide-phosphate, a known intermediate of the de novo biosynthetic pathway. The existence of an adenosylcobinamide amidohydrolase enzyme would explain the lack of an adenosylcobinamide kinase in archaea.

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“…CbiH of S. typhimurium has recently been shown to be responsible for C-17 methylation of cobalt-precorrin 3 (Fig. 2a), leading to formation of the ring-contracted, lactonized intermediate, cobalt-precorrin 4 (Santander et al, 1997). Although the function of CbiG is unknown, the occurrence of CbiG and CbiH as a single enzyme in two different organisms suggests that CbiG may operate either immediately before or immediately after CbiH.…”

Section: Isolation and Sequence Of P Freudenreichii Vitamin B 12 Biomentioning

confidence: 99%

Isolation and characterization of 14 additional genes specifying the anaerobic biosynthesis of cobalamin (vitamin B12) in Propionibacterium freudenreichii (P. shermanii) The GenBank accession numbers for the sequences reported in this paper are AY033235, AY033236, U13043 and U51164.

et al. 2002

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A search for genes encoding enzymes involved in cobalamin (vitamin B 12 ) production in the commercially important organism Propionibacterium freudenreichii (P. shermanii) has resulted in the isolation of an additional 14 genes encoding enzymes responsible for 17 steps of the anaerobic B 12 pathway in this organism. All of the genes believed to be necessary for the biosynthesis of adenosylcobinamide from uroporphyrinogen III have now been isolated except two (cbiA and an as yet unidentified gene encoding cobalt reductase). Most of the genes are contained in two divergent operons, one of which, in turn, is closely linked to the operon encoding the B 12 -dependent enzyme methylmalonyl-CoA mutase. The close linkage of the three genes encoding the subunits of transcarboxylase to the hemYHBXRL gene cluster is reported. The functions of the P. freudenreichii B 12 pathway genes are discussed, and a mechanism for the regulation of cobalamin and propionic acid production by oxygen in this organism is proposed.

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How corrinoids are synthesized without oxygen: nature's first pathway to vitamin B12

Cited by 54 publications

References 20 publications

ThecobYGene of the ArchaeonHalobacteriumsp. Strain NRC-1 Is Required for De Novo Cobamide Synthesis

ThecobYGene of the ArchaeonHalobacteriumsp. Strain NRC-1 Is Required for De Novo Cobamide Synthesis

A New Pathway for Salvaging the CoenzymeB₁₂Precursor Cobinamide in Archaea RequiresCobinamide-Phosphate Synthase (CbiB) EnzymeActivity

Isolation and characterization of 14 additional genes specifying the anaerobic biosynthesis of cobalamin (vitamin B12) in Propionibacterium freudenreichii (P. shermanii) The GenBank accession numbers for the sequences reported in this paper are AY033235, AY033236, U13043 and U51164.

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How corrinoids are synthesized without oxygen: nature's first pathway to vitamin B12

Cited by 54 publications

References 20 publications

ThecobYGene of the ArchaeonHalobacteriumsp. Strain NRC-1 Is Required for De Novo Cobamide Synthesis

ThecobYGene of the ArchaeonHalobacteriumsp. Strain NRC-1 Is Required for De Novo Cobamide Synthesis

A New Pathway for Salvaging the CoenzymeB12Precursor Cobinamide in Archaea RequiresCobinamide-Phosphate Synthase (CbiB) EnzymeActivity

Isolation and characterization of 14 additional genes specifying the anaerobic biosynthesis of cobalamin (vitamin B12) in Propionibacterium freudenreichii (P. shermanii) The GenBank accession numbers for the sequences reported in this paper are AY033235, AY033236, U13043 and U51164.

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A New Pathway for Salvaging the CoenzymeB₁₂Precursor Cobinamide in Archaea RequiresCobinamide-Phosphate Synthase (CbiB) EnzymeActivity