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Folic acid biosynthesis Organism: ..
The E. coli metF gene product is involved in the folate branch of the methionine biosynthetic pathway (). It catalyzes the reduction of N5,10-methylenetetrahydrofolate to N5-methyltetrahydrofolate, which in turn gives its methyl group to homocysteine in order to form methionine, in a reaction catalyzed by either a vitamin B12-dependent methyltransferase (the metH gene product) or a vitamin B12-independent methyltransferase (the metE gene product).
We examine here the biosyntheticpathways of purine and pyrimidine nucleotides and their regulation, theformation of the deoxynucleotides, and the degradation of purines andpyrimidines to uric acid and urea.
Biosynthesis of folic acid | SpringerLink
The nucleotide sequence of this DNA fragment revealed the presence of three open reading frames (ORF), two of which (ORF1 and ORF3) were incomplete. Compared with proteins in the SWISS-PROT database, the product of ORF1 displayed high homology with the Bacillus subtilis thiC gene product, which is involved in thiamine biosynthesis (), and the product of ORF3 showed homology with a hypothetical 10.2-kDa B. subtilis membrane protein. The protein encoded by ORF2 showed strong homology with MetF proteins of E. coli (34.5% identical amino acids), S. typhimurium (33.8% identity), and Haemophilus influenzae (34.6% identity) (Fig. ). The metF gene product (5,10-methylenetetrahydrofolate reductase) is involved in the folate branch of the methionine biosynthesis pathway. The gene encoded by ORF2 was tentatively designated metF.
Genes homologous to metF have been found in other gram-negative bacteria, such as S. typhimurium () and H. influenzae (). However, this is the first time that a metF homolog has been found in a gram-positive bacterium. Its involvement in methionine biosynthesis has been proved by gene disruption that resulted in methionine auxotrophy. Growth of the disrupted mutant was restored by transformation with an undisrupted metF-containing plasmid (pVKK-metF). These results indicate that the folate branch is essential to provide the methyl group of methionine in actinomycetes. Synthesis of the folic acid moiety by the formyl tetrahydrofolate synthetase has been reported recently in Streptococcus mutans, another gram-positive bacterium ().
Folic Acid Synthesis Inhibitors - SlideShare
Folate coenzymes are responsible for the following important metabolic functions: 1) Formation of purines and pyrimidines which, in turn, are needed for synthesis of the nucleic acids DNA and RNA. 2) Formation of heme, the iron-containing protein in hemoglobin, 3) Interconversion of the 3-carbon amino acid serine from the 2-carbon amino acid glycine, 4) Formation of the amino acids tyrosine from phenylalanine and glutamic acid from histidine, 5) Formation of the amino acid methionine from homocysteine (Vitamin B12 as methylcobalamin also is needed for this conversion). Elevated levels of homocysteine have been implicated in a wide range of health disorders. In the reconversion of homocysteine to methionine the body uses the methionine to make the important amino acid s-adenosylmethionine (SAMe) which is known to be helpful in cases of depression, 6) Synthesis of choline from ethanolamine, 7) Formation and maturation of red and white blood cells, and 8) Conversion of nicotinamide to N'-methylnicotinamide.
In E. coli and S. typhimurium, the methyl group of N5-methyltetrahydrofolate derives necessarily from N5,10-methylenetetrahydrofolate, an intermediate of the so-called folate branch of the methionine pathway (). It is unclear, however, whether the same pathway occurs in Streptomyces species or other gram-positive bacteria. In this paper, we report the cloning and characterization of the Streptomyces lividans metF homolog and its involvement in methionine biosynthesis.
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Synonyms: folic acid biosynthesis, ..
Examination of the aromatic aminoacid biosynthesis pathway in Chlamydia trachomatis revealed that the chorismate biosynthesis portion of the pathway was intact, however most enzymes necessary for the conversion of chorsimate to the 3 branch aromatic aminoacids were not present (only tyrB, trpA/B and trpF have been identified in Chlamydia trachomatis). This truncated aromatic amino acid biosynthesis pathways in Chlamydia trachomatis give rise to end product -chorismate that are used as intermediates for other biosynthetic pathways. So the ubiquinone, folate, menaquinone and enterobactin biosynthesis pathway have been searched in Chlamydia trachomatis. About half of the ubiquinone and folate biosynthesis pathways genes appear in Chlamydia trachomatis, however almost all of genes for menaquinone and enterobactin biosynthesis are missing. In folic acid biosyntheses pathway, Chlamydia trachomatis is missing pabA, pabB (encoding aminodeoxychorismate synthase) and pabC (encoding aminodeoxychorismate lyase), which catalyze the reaction from chorismate to p-aminobenzoate. We suppose this means that Chlamydia trachomatis might depend on the host to supply PABA for folic acid biosynthesis. In ubiquinone biosynthesis pathway, Chlamydiae trachomatis contain homologs of ubiA (encoding 4-hydroxybenzoate octaprenyltransferase); ubiX (encoding 3-octaprenyl-4-hydroxybenzoate decarboxylase) and ubiE (2-octaprenyl-6-methoxy-1, 4-benzoquinone methylase), the genes encoding the rest 5 steps of reactions are missing.
It is very interesting that the chorismate biosynthetic pathway genes in CT are in the same operon except the first gene aroA is at difference place. In many microbial eukaryotes, the aroM gene from fungi encodes a single polypeptide that catalyses five consecutive steps of the chorismate biosynthetic pathway. If the genes encoding enzymes in the common-pathway portion of aromatic biosynthesis are named in order of reaction sequence (i.e., aroA-aroG), the domain order in aroM gene is aroB*aroF*aroE*aroC*aroD.
Folic Acid is Hazardous to Your Health. What About …
Folic acid, also known as Vitamin B9 is important to several biological functions. The folate derivative, 5,10-methylene-tetrahydrofolate is essential for the synthesis of dTMP from dUMP and it is therefore crucial for DNA replication and cell division. Tetrahydrofolate is an essential substrate in the biosynthesis of amino acid, glycine. Drugs targeting folate biosynthesis pathway has long been prescribed as anti-malarial agents. The two essential precursors of folate biosynthesis are 4-aminobenzoate (a product of pathway) and GTP. Thymidylate cycle, a part of folate biosynthesis pathway (below) plays important role in the generation of amino acid glycine and dTMP. Dihydrofolate reductase enzyme replenishes tetrahydrofolate from dihydrofolate for the above mentioned biosynthetic processes. The dihydrofolate reductase and thymidylate synthase activities are catalysed by a bifunctional enzyme in both Plasmodium falciparum and Toxoplasma gondii. In addition to the de novo folate biosynthesis pathway, T. gondii can salvage folate from host. Massimine et al demonstrated the uptake of radio-labelled exogenous folic acid and revealed the presence of common folate transporter which has high affinity for folic acid. This transporter is suggested to be bidirectional and concentration-dependent. They also added that T. gondii and other apicomplexans encode folate transporters as there are putative transporters homologous to BT1 family proteins present in these Apicomplexa genomes .
but a major folic acid derivative biosynthesis pathway.
T. gondii also possesses the enzymes for the synthesis of tetrahydrobiopterin and dihydrobiopterin. Tetrahydrobiopterin is an important cofactor in the hydroxylation of phenylalanine to tyrosine (catalysed by the enzyme phenylalanine hydroxylase), a reaction which is present in T. gondii () and absent in P. falciparum. The enzymes 220.127.116.11 (catalyses conversion of 6-pyruvoyl-5,6,7,8-tetrahydropterin into tetrahydrobiopterin) and 18.104.22.168 (converts dihydrobiopterin to tetrahydrobiopterin) are absent in P. falciparum (Refer to pathway in MPMP). The two aromatic amino acid hydroxylase enzymes present in T. gondii genome utilises tetrahydrobiopterin as cofactor. Homology-based search has also led to the identification of five enzymes catalysing biosynthesis of molybdopterin from GTP. Sulfite oxidase, an enzyme utilising molybdopterin as cofactor is also present in T. gondii.
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