On the Methylation Process and Cobalt Insertion in Cobyrinic Acid Biosynthesis

Müller, Gerhard; Hlineny, Kersten; Savvidis, Eleftherios; Zipfel, Franz; Schmiedl, J.; Schneider, Erich

doi:10.1007/978-1-4757-9637-7_22

Cited by 13 publications

(15 citation statements)

References 27 publications

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“…When AR8830 was grown in the presence of cobalt, no such intermediates could be detected but high levels of cobyric acid were obtained (Table 3; also see above). The accumulation of factors II and III in the absence of cobalt is thus similar to what has been observed with Propionibacterium shermanii (7,8,33).…”

Section: Analysis Of the 29 Isolated S Typhimurium Cob Mutants The supporting

confidence: 82%

“…However, it seems likely that cobK and cbiJ are in fact similar (see below). These comparative genome studies, together with observations made with Propionibacterium shermanii (5,34,35) and other species, suggest that there is more than one pathway for corrin biosynthesis (11,48). The differences relate to the timing of the cobalt insertion and the method of ring contraction.…”

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confidence: 80%

“…The differences relate to the timing of the cobalt insertion and the method of ring contraction. Thus, in S. typhimurium the cobalt may be inserted at an early stage of the biosynthesis, before the synthesis of precorrin-3, as in Propionibacterium shermanii (5,34,35), rather than at a later stage, after the synthesis of hydrogenobyrinic acid a,c-diamide, as it has been shown in P. denitrificans (22).…”

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confidence: 84%

“…The oxidized intermediates were identified on the basis of their UV and visible spectra, with maxima at A 376 and A 407 and mass spectra as follows: factor III dilactone, M ϩ 1 ϭ 957; factor II dilactone, M ϩ 1 ϭ 945) (Fig. 8 and data not shown) (7,33). When AR8830 was grown in the presence of cobalt, no such intermediates could be detected but high levels of cobyric acid were obtained (Table 3; also see above).…”

Section: Analysis Of the 29 Isolated S Typhimurium Cob Mutants The mentioning

confidence: 99%

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Salmonella typhimurium cobalamin (vitamin B12) biosynthetic genes: functional studies in S. typhimurium and Escherichia coli

et al. 1996

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In order to study the Salmonella typhimurium cobalamin biosynthetic pathway, the S. typhimurium cob operon was isolated and cloned into Escherichia coli. This approach has given the new host of the cob operon the ability to make cobalamins de novo, an ability that had probably been lost by this organism. In total, 20 genes of the S. typhimurium cob operon have been transferred into E. coli, and the resulting recombinant strains have been shown to produce up to 100 times more corrin than the parent S. typhimurium strain. These measurements have been performed with a quantitative cobalamin microbiological assay which is detailed in this work. As with S. typhimurium, cobalamin synthesis is only observed in the E. coli cobalamin-producing strains when they are grown under anaerobic conditions. Derivatives of the cobalamin-producing E. coli strains were constructed in which genes of the cob operon were inactivated. These strains, together with S. typhimurium cob mutants, have permitted the determination of the genes necessary for cobalamin production and classification of cbiD and cbiG as cobI genes. When grown in the absence of endogenous cobalt, the oxidized forms of precorrin-2 and precorrin-3, factor II and factor III, respectively, were found to accumulate in the cytosol of the corrinproducing E. coli. Together with the finding that S. typhimurium cbiL mutants are not complemented with the homologous Pseudomonas denitrificans gene, these results lend further credence to the theory that cobalt is required at an early stage in the biosynthesis of cobalamins in S. typhimurium.

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Section: Analysis Of the 29 Isolated S Typhimurium Cob Mutants The supporting

confidence: 82%

mentioning

confidence: 80%

mentioning

confidence: 84%

Section: Analysis Of the 29 Isolated S Typhimurium Cob Mutants The mentioning

confidence: 99%

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Salmonella typhimurium cobalamin (vitamin B12) biosynthetic genes: functional studies in S. typhimurium and Escherichia coli

et al. 1996

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“…Experiments with partially purified extracts from P. freudenreichii provided the earliest evidence that urogen III methyl-transferase catalyzes both methylation steps to form precorrin-2 from urogen III (17). Since CysG has been shown to insert not only iron but also cobalt into factor II, it has been suggested (31) that urogen III methyltransferase in P. freudenreichii may also be a CysG-like enzyme that could synthesize a cobalt-containing analog of siroheme as an early intermediate.…”

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Cloning, sequencing, and expression of the uroporphyrinogen III methyltransferase cobA gene of Propionibacterium freudenreichii (shermanii)

et al. 1995

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We cloned, sequenced, and overexpressed cobA, the gene encoding uroporphyrinogen III methyltransferase in Propionibacterium freudenreichii, and examined the catalytic properties of the enzyme. The methyltransferase is similar in mass (27 kDa) and homologous to the one isolated from Pseudomonas denitrificans. In contrast to the much larger isoenzyme encoded by the cysG gene of Escherichia coli (52 kDa), the P. freudenreichii enzyme does not contain the additional 22-kDa peptide moiety at its N-terminal end bearing the oxidase-ferrochelatase activity responsible for the conversion of dihydrosirohydrochlorin (precorrin-2) to siroheme. Since it does not contain this moiety, it is not a likely candidate for synthesis of a cobalt-containing early intermediate that has been proposed for the vitamin B 12 biosynthetic pathway in P. freudenreichii. Uroporphyrinogen III methyltransferase of P. freudenreichii not only catalyzes the addition of two methyl groups to uroporphyrinogen III to afford the early vitamin B 12 intermediate, precorrin-2, but also has an overmethylation property that catalyzes the synthesis of several tri-and tetra-methylated compounds that are not part of the vitamin B 12 pathway. The enzyme catalyzes the addition of three methyl groups to uroporphyrinogen I to form trimethylpyrrocorphin, the intermediate necessary for biosynthesis of the natural products, factors S1 and S3, previously isolated from this organism. A second gene found upstream from the cobA gene encodes a protein homologous to CbiO of Salmonella typhimurium, a membrane-bound, ATP-dependent transport protein thought to be part of the cobalt transport system involved in vitamin B 12 synthesis. These two genes do not appear to constitute part of an extensive cobalamin operon.Uroporphyrinogen (urogen) III methyltransferase, a key enzyme in the biosynthetic pathways of vitamin B 12 and siroheme, catalyzes the S-adenosyl-L-methionine (SAM)-dependent bismethylation of its substrate, urogen III, resulting in the formation of dihydrosirohydrochlorin (known as precorrin-2 in the vitamin B 12 pathway). In the biosynthesis of vitamin B 12 in the anaerobe Propionibacterium freudenreichii, labeling experiments have indicated that cobalt is inserted soon after the formation of precorrin-2 (3, 20), and the recent isolation of a cobalt-containing tetramethylated corphinoid, possibly an intermediate, from this organism supports these observations (3). Cobalt insertion in the vitamin B 12 pathway of the aerobe Pseudomonas denitrificans, however, occurs at a much later stage with insertion into hydrogenobyrinic acid diamide (6).Urogen III methyltransferase has been purified to homogeneity from several different organisms, and the nucleotide sequences of the corresponding genes have been determined, revealing that the enzyme exists in at least two forms. One form, encoded by the cysG gene, is required for siroheme and, thus, for cysteine synthesis in Escherichia coli (14,31,35) and siroheme and vitamin B 12 synthesis in Salmonella typhimurium (8, 10). The ...

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