Glycosylated forms of pyridoxine, vitamin D, niacin, pantothenate, and riboflavin exist in nature, whereas glycosides of retinol and ascorbic acid are products of in vitro transglycosidation. Beta-Glucosides of pyridoxine (a) are prevalent in plant-derived foods, (b) contribute to human nutrition as partially available sources of vitamin B6, (c) undergo partial hydrolysis by a novel mammalian cytosolic beta-glucosidase, and (d) exert a weak antagonistic effect on the utilization of free pyridoxine. Niacin exists in grains as complexed forms with low bioavailability, whereas vitamin D glycosides are toxic components of certain calcinogenic plants of importance in animal health. Glycosides of pantothenate and riboflavin appear to be minor products of mammalian metabolism. Glycosylation of retinol or other hydrophobic alcohols may facilitate glycolipid turnover, whereas a stable ascorbyl glucoside may have nutritional applications. Glycosylation of vitamins exerts widely ranging chemical and biological effects, with great nutritional and metabolic significance.

Nutritional properties and significance of vitamin glycosides

We report that pdxA, which is required for de novo biosynthesis of pyridoxine (vitamin B6) and pyridoxal phosphate, belongs to an unusual, multifunctional operon. The pdxA gene was cloned in the same 3.5-kilobase BamHI-EcoRI restriction fragment that contains ksgA, which encodes the 16S rRNA modification enzyme m6(2)A methyltransferase, and apaH, which encodes diadenosine tetraphosphatase (ApppA hydrolase). Previously, Blanchin-Roland et al. showed that ksgA and apaH form a complex operon (Mol. Gen. Genet. 205:515-522, 1986). The pdxA gene was located on recombinant plasmids by subcloning, complementation, and insertion mutagenesis, and chromosomal insertions at five positions upstream from ksgA inactivated pdxA function. DNA sequence analysis and minicell translation experiments demonstrated that pdxA encoded a 35.1-kilodalton polypeptide and that the stop codon of pdxA overlapped the start codon of ksgA by 2 nucleotides. The translational start codon of pdxA was tentatively assigned based on polypeptide size and on the presence of a unique sequence that was also found near the translational start of PdxB. This conserved sequence may play a role in translational control of certain pyridoxine biosynthetic genes. RNase T2 mapping of chromosomal transcripts confirmed that pdxA and ksgA were members of the same complex operon, yet about half of ksgA transcripts arose in vivo under some culture conditions from an internal promoter mapped near the end of pdxA. Transcript analysis further suggested that pdxA is not the first gene in the operon. These structural features support the idea that pyridoxine-biosynthetic genes are members of complex operons, perhaps to interweave coenzyme biosynthesis genetically with other metabolic processes. The results are also considered in terms of ksgA expression.

Overlap between pdxA and ksgA in the complex pdxA-ksgA-apaG-apaH operon of Escherichia coli K-12.

Triumbellin, a tricoumarin rhamnopyranoside from Daphne mezereum

Methods for determination of vitamin B6foods and other biological materials: A critical review☆

B 6 -vitamiini (pyridoksiini) on vesiliukoinen vitamiini,joka esiintyy erilaisissa kemiallisissa muodoissa biologisissa materiaaleissa kuten elainkudoksissa, kasvisolukoissa ja niita sisaltavissa elintarvikkeissa. Elimistossa B 6 -vitamiini edesauttaa monia biokemiallisia reaktioita mm. valkuaisaineiden ja glykogeenin aineenvaihdunnassa. Perinteisen vitamiinivaikutuksen lisaksi pyridoksiini saattaa liittya mm. altistumiseen sydan- ja verisuonitaudeille. Tieteellista nayttoa naista uusista yhteyksista ei kuitenkaan viela ole saatu. Perinteisesti B 6 -vitamiini on maaritetty elintarvikkeista mikrobiologisesti, jolloin pyridoksiini on vapautettu ns. sidotuista muodoista. Tassa tyossa selvitettiin nestekromatografian (HPLC:n) soveltuvuutta B 6 -vitamiinin vapaiden ja sidottujen muotojen maarittamiseen elintarvikkeista. Kehitetyn menetelman luotettavuus varmistettiin mm. Euroopan unionin jarjestamissa laboratorioiden valisissa vertailututkimuksissa. Menetelmalla maaritettiin 50 elintarvikenimikkeen eri B 6 -vitamiinimuotojen pitoisuudet. Runsaasti pyridoksiinia tai sen johdannaisia sisalsivat mm. liha ja sisaelimet (maksa ja munuaiset), kananmunan keltuainen ja hasselpahkina. Kasviperaisten elintarvikkeiden B 6 -vitamiini koostui suurelta osin sidotuista glykosyloiduista vitamiinimuodoista. Niiden hyvaksikaytettavyydesta elimistossa on varsin ristiriitaisia tietoja. Tyossa saadut elintarvikkeiden B 6 -vitamiinitulokset liitetaan Kansanterveyslaitoksen elintarvikkeiden koostumustietopankkiin ja niita hyodynnetaan mm. ravitsemussuunnittelussa. Tyo osoitti olevan tarpeellista yhdenmukaistaa kaytettavia maaritysmenetelmia, jotta eri laboratorioissa saadut tulokset olisivat paremmin vertailukelpoisia. Tata menetelmien yhtenaistamista jatketaan mm. Euroopan Standardoimisliiton (CEN) tyoryhmissa.

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HPLC analysis of vitamin B6 in foods

A new derivative of pyridoxine was formed from PN in seedlings of podded pea, Pisum sativum L. cv. Kinusaya, together with 5'-O-(beta-D-glucopyranosyl)pyridoxine and 5'-O-[6-O-(3-hydroxy-3-methyl-4-carboxybutanoyl)-beta-D-glucopyran osyl] pyridoxine. The compound was isolated and identified as 5'-O-(6-O-malonyl-beta-D-glucopyranosyl)pyridoxine.

Isolation and structure of a minor metabolite of pyridoxine in seedlings of Pisum sativum L.

Isolation and Structure of a New Metabolite of Pyridoxine in Seedlings of Pisum sativum L. Kenjiro Tadera, Kyoko Nagano, Fumio Yagi, Akira Kobayashi, Kiyohisa Imada & Shunichiro Tanaka To cite this article: Kenjiro Tadera, Kyoko Nagano, Fumio Yagi, Akira Kobayashi, Kiyohisa Imada & Shunichiro Tanaka (1983) Isolation and Structure of a New Metabolite of Pyridoxine in Seedlings of Pisumsativum L., Agricultural and Biological Chemistry, 47:6, 1357-1359, DOI: 10.1080/00021369.1983.10863889 To link to this article: https://doi.org/10.1080/00021369.1983.10863889

Kiyohisa Imada

Papers

Isolation and structure of a minor metabolite of pyridoxine in seedlings of Pisum sativum L.

Isolation and Structure of a New Metabolite of Pyridoxine in Seedlings of Pisum sativum L.