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PubMed1999

[Vitamin B6].

1934, vitamin B6 was discovered by P. György. Vitamin B6 consists of 3 closely related pyrimidine derivatives: pyridoxine, pyridoxal and pyridoxamine and their phosphate esters. The tumor-specific compound has been recently found to be as a new B6 derivatives. The active form of vitamin B6 is pyridoxal phosphate (PLP) which is produced by multi-metabolizing enzymes including pyridoxine kinase and PNP/PMP oxidase. PLP functions as the coenzymes of many enzymes which catalyze biochemical reactions such as transamination and decarboxylation. A novel physiological function of PLP which is the negative modulator of the steroid-dependent gene expression and the albumin gene expression has been also revealed.

Animals↗
PubMed1975

The influence of antiepileptic drugs on vitamin B6 metabolism.

Vitamin B6 nutriture was measured by means of determination of activity of EGOT in 30 and of serum pyridoxal phosphate in 27 epileptic children under antiepileptic treatment with various antiepileptic drugs and with hydantoin and succinimide alone, 25 healthy infants and children were controls. Under the treatment with antiepileptic drugs, especially with hydantoin and succinimide a depression of the activity of EGOT and the level of pyridoxal-phosphate in serum followed. As an induction of vitamin B6 dependnet enzyme activity can be excluded a possible explanation for the disturbance in vitamin B6 metabolism could be the inhibition of activity of pyridoxalkinase. We consider the administration of vitamin B6 in addition to hydantoin and succinimide as appropriate.

Anticonvulsants↗
PubMed2006

Analysis of the Arabidopsis rsr4-1/pdx1-3 mutant reveals the critical function of the PDX1 protein family in metabolism, development, and vitamin B6 biosynthesis.

Vitamin B6 represents a highly important group of compounds ubiquitous in all living organisms. It has been demonstrated to alleviate oxidative stress and in its phosphorylated form participates as a cofactor in >100 biochemical reactions. By means of a genetic approach, we have identified a novel mutant, rsr4-1 (for reduced sugar response), with aberrant root and leaf growth that requires supplementation of vitamin B6 for normal development. Cloning of the mutated gene revealed that rsr4-1 carries a point mutation in a member of the PDX1/SOR1/SNZ (for Pyridoxine biosynthesis protein 1/Singlet oxygen resistant 1/Snooze) family that leads to reduced vitamin B6 content. Consequently, metabolism is broadly altered, mainly affecting amino acid, raffinose, and shikimate contents and trichloroacetic acid cycle constituents. Yeast two-hybrid and pull-down analyses showed that Arabidopsis thaliana PDX1 proteins can form oligomers. Interestingly, the mutant form of PDX1 has severely reduced capability to oligomerize, potentially suggesting that oligomerization is important for function. In summary, our results demonstrate the critical function of the PDX1 protein family for metabolism, whole-plant development, and vitamin B6 biosynthesis in higher plants.

Amino Acid Sequence↗
PubMed1985

Stability of pyridoxal-5-phosphate semicarbazone: applications in plasma vitamin B6 analysis and population surveys of vitamin B6 nutritional status.

The determination of pyridoxal-5-phosphate (PLP) and pyridoxal (PL) in plasma requires the availability of dark room facilities, due to the photosensitivity of these vitamin B6 vitamers. The fact that the semicarbazone forms of PL and PLP are more strongly fluorescent than the underivatized B6 vitamers has been exploited in plasma analyses, but it was not previously realised that these semicarbazone forms are also very stable even under conditions that lead to rapid decomposition of free PL and PLP. The stabilisation of PLP and PL obtained in this manner is sufficient and fully adequate to meet the practical requirements of clinical field studies. We report a high-performance liquid chromatographic method for plasma PLP and PL determinations based on precolumn semicarbazone formation and fluorescence detection. The method is sensitive enough for quantitative plasma PLP determinations even in B6-deficient patients.

Chromatography, High Pressure Liquid↗
PubMed2001

Effect of exercise on the metabolism of vitamin B6 and some PLP-dependent enzymes in young rats fed a restricted vitamin B6 diet.

The effect of exercise on vitamin B6 metabolism and PLP-dependent enzymes was studied in rats fed a diet with or without vitamin B6. Metabolism of some amino acids (citrulline, arginine, ornithine and threonine) inhibited in the B6-deficient rats was normalized during exercise. Exercise was also effective in storing vitamin B6 in the body by lowering excretion of vitamin B6, when intake of vitamin B6 was restricted. Aspartatae aminotransferase activity was higher in the red portion of the gastrocnemius muscle than that of the white one, whereas glycogen phosphorylase activity was vice versa and furthermore glycogen content in the white portion was very low in the vitamin B6-deficient rat. From the data obtained, it has been suggested that the red and white portions of the gastrocnemius muscle seemed to be more important in metabolizing amino acids and hydrolyze glycogen, respectively.

Adaptation, Physiological↗
PubMed1985

Differences in vitamin B6 status indicator responses between young and middle-aged women fed constant diets with two levels of vitamin B6.

The responses of adult women to two levels of vitamin B6, was conducted with five young and eight middle-aged subjects. A constant diet (2.3-2.4 mg vitamin B6 per day) was fed for four weeks followed by three weeks of the same diet supplemented with 8.0 mg pyridoxine. Plasma pyridoxal 5'-phosphate (PLP), plasma and urinary vitamin B6, and urinary 4-pyridoxic acid (4-PA) were determined. The older women had significantly lower plasma PLP, plasma and urinary vitamin B6 and slightly higher urinary 4-PA values on normal vitamin B6 intakes. With supplementation, only the difference in urinary total vitamin B6 remained significant. Tryptophan load tests revealed no significant between-group differences in xanthurenic acid or kynurenic acid excretion. These results demonstrate an age-related difference in vitamin B6 status indicators in women under controlled dietary intake of vitamin B6.

Adult↗
PubMed1989

[The course of vitamin B6 content in growing rats during vitamin B6-free nutrition].

This experiment was designed in two parts. In the first part the vitamin B6 efficiency in response to increasing dietary vitamin B6 intakes was tested in growing rats; in the second part the reaction of rats, originally supplied with the fourfold requirement and then switched on the vitamin-B6-free basal diet was examined. The experimental animals were male Sprague-Dawley rats, of which weight gains, feed intake, and vitamin-B6-concentrations in blood, liver and whole carcass were measured. At the beginning of the trial nine animals were analyzed; 54 additional animals, divided into six groups, were given a vitamin-B6-free semisynthetic diet for three weeks which was supplemented with 0, 1.5, 3, 6, 12, and 24 mg vitamin B6 per kg feed. For the second part the additional 54 animals were given a diet with 24 mg vitamin B6 for three weeks and then switched to the vitamin-B6-free basal diet. Six animals per group were sacrificed after 2, 5, 8, 12, 16, 20, 25, 30, and 35 days of depletion. Efficiency of dietary vitamin B6 decreased from 38% at 1.5 mg vitamin B6 per kg diet to 4% at the 24 mg dietary level. Also, without dietary vitamin B6 the animals gained weight (from 145 to 300 g live weight), the daily feed intake increased from 14 to 19 g and feed efficiency decreased from 2.2 to 4.3 g feed per g gain. Vitamin B6 concentration in tissues reacted differently.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗