El piridoxal 5'-fosfato es la forma biocatalíticamente activa de la vitamina B6, siendo uno de los cofactores más versátiles de la naturaleza, el cuál tiene un papel central en el metabolismo de aminoácidos. Mientras que la mayoria de microorganismos y plantas pueden sintetizar la vitamina B6 de novo, los mamíferos se ven obligados a obtener uno de sus vitámeros a través de la dieta. La maquinaria biosintética de Escherichia coli es, de lejos, la mejor caracterizada y consiste en cuatro proteínas pdx. PdxJ, también conocida como piridoxina 5'-fosfato sintasa, es la enzima clave en esta via. Cataliza el último paso, la complicada reacción de cierre del anillo entre 1-deoxi-D-xilulosa-5-fosfato y aminoacetona-3-fosfato para formar piridoxina 5'-fosfato. La comparación de secuencias de PdxJ entre espécies revela que existe un alto grado de conservación indicando así la enorme importancia fisiológica de esta enzima.Con el uso de un derivado de mercurio fue posible el resolver la estructura cristalina de la enzima de E. coli por el método del "single isomorphous replacement with anomalous scattering" y el refinar la estructura a 2.0 Å de resolución. El monómero corresponde al plegamiento TIM o barril (_/_)8, con la incorporación de tres hélices extra que median los contactos entre intersubunidades en el octámero. El octámero representa el estado fisiológicamente relevante, que fué observado tanto en el cristal como en solución, y que esta organizado como un tetrámero de dímeros activos. La caracterización de la estructura cristalográfica de la enzima con sustratos, análogos de sustrato y productos unidos permitió la identificación del centro activo y la propuesta de un mecanismo detallado. Los rasgos catalíticos más remarcables son: (1) el cierre del centro activo una vez se han unido los sustratos, de manera que el bolsillo de unión queda aislado del solvente y los intermediarios de la reacción quedan así estabilizados; (2) la existencia de dos sitios de unión de fosfato bien definidos; (3) y un canal de agua que penetra el núcleo del barril _ y permite liberar las moléculas de agua formadas durante la reacción.La cantidad de información presentada debería permitir el diseño de inhibidores de la piridoxina 5'-fosfato sintasa basados en su estructura. Es interesante el destacar que entre las bacterias que contienen el gen pdxJ se encuentran unos cuantos patógenos bien conocidos. La resistencia de bacterias contra antibióticos está aumentando cada vez más, hecho que se está convirtiendo en un auténtico problema. Por este motivo, es necesario el desarrollar medicamentos antibacterianos con un alto grado de especificidad y la piridoxina 5'-fosfato sintasa parece ser una diana muy prometedora. / Pyridoxal 5'-phosphate is the biocatalytically active form of vitamin B6, being one of nature's most versatile cofactors that plays a central role in the metabolism of amino acids. Whereas microorganisms and plants can synthetise vitamin B6 de novo, mammals have to obtain one of the B6 vitamers with their diet. The Escherichia coli biosynthetic machinery is the, by far, best characterised and it consists in four pdx proteins. PdxJ, also referred to as pyridoxine 5'-phosphate synthase, is the key enzyme in this pathway. It catalyses the last step, the complicated ring-closure reaction between 1-deoxy-D-xylulose-5-phosphate and aminoacetone-3-phosphate yielding pyridoxine 5'-phosphate. Sequence comparison of PdxJ from different species revealed a remarkable high degree of conservation indicating the paramount physiological importance of this enzyme.With the use of one mercury heavy-atom derivative, it was possible to solve the crystal structure of the E. coli enzyme by the single isomorphous replacement method with anomalous scattering and to refine the structure at 2.0 Å resolution. The monomer folds as a TIM or (_/_)8 barrel, with the incorporation of three extra helices that mediate intersubunits contacts within the octamer. The octamer represents the physiological relevant state that was observed in the crystal and in solution, and that is organised as a tetramer of active dimers. Characterisation of the enzyme crystal structure with bound substrates, substrate analogues, and products allowed the identification of the active site and the proposal of a detailed reaction mechanism. The most important catalytic features are: (1) active site closure upon substrate binding, in order to isolate the specificity pocket from the solvent und thus stabilise the reaction intermediates; (2) the existence of two well-defined phosphate binding sites; (3) and a water channel that penetrates the _ barrel core and allows the release of waters in the closed state.The amount of information here presented should permit the structure-based design of pyridoxine 5'-phosphate synthase inhibitors. Interestingly, among bacteria that contain the pdxJ gene there are several well-known pathogens. More and more, the bacterial resistance against antibiotics is increasing and therefore becoming a real problem. Thus, it is necessary the development of highly specific antibacterial drugs and pyridoxine 5'-phosphate synthase seems to be a promising novel target.

Vitamin B-6 is a vitamin often promoted by the popular press as a cure all. It's role is also being studied in regard to pre-menstrual syndrome, myocardial infarction and alterations in lipid and fatty acid metabolism. This study was designed to investigate whether there was a difference between vitamin B-6 blood levels, during a baseline study, a period of vitamin B-6 depletion and vitamin B-6 supplemention in ten men ages 21-37. The effect of each diet on total cholesterol was also investigated.The experimentally accessible population for this study Laboratory as part of a larger study conducted by Dr. Stephen Coburn of the Fort Wayne State Developmental Center.Analysis of the data indicated:1) A significant difference between red blood cell pyridoxal phosphate and blood plasma levels of vitamin B-6 during the baseline, depletion and supplementation phases in ten men 21-37.2) Total serum cholesterol levels fell significantly through all phases of the study. High density lipoproteins fell significantly during the depletion phase but did not rise significantly during the supplementation phase. Low density lipoproteins showed no significant difference during the three phases of the study. When dietary records were evaluated mean dietary intake during the baseline and supplementation phases of the diet met the Recommended Dietary Allowance (RDA) for vitamin B-6. Mean protein intake also met the RDA with 102.1 grams during the baseline phase and 106.1 grams during the supplementation phase. These intakes are consistent with those found in previous studies conducted by the USDA. Mean intake of fat was lower than the 30 percent of calories recommended by the American Heart Association but wide variation existed among subjects.No physical symptoms of vitamin B-6 deficiency manifested themselves during the study. Subjects reported no other problems associated with low vitamin B-6 intakes.The data indicated that vitamin B-6 intake effects the amount of red blood cell plasma pyridoxal phosphate and plasma vitamin B-6. No clear effect can be found between vitamin B-6 intake and serum cholesterol levels. "Normal" diets also appeared to provide adequate vitamin B-6 to meet both RDA's and somatic needs. Wide variation seems to exist, however, among individuals. / Department of Home Economics

Graduation date: 1999

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

abstract: Oral contraceptives are one of the most frequently used forms of birth control among young women. However, research has shown that this type of medication can contribute to negative changes in mood and diminished vitamin status. In particular, women taking oral contraceptives are at an increased risk of vitamin B6 deficiency due to changes in enzyme activity with estrogen intake. Depressed mood is one of the known symptoms of vitamin B6 deficiency as this vitamin acts as an essential cofactor in converting tryptophan to the neurotransmitter, serotonin. Lack of adequate levels of vitamin B6 therefore contribute to decreased production of serotonin and subsequent changes in mood, including symptoms of depression. With vitamin B6 being the most common nutrient deficiency, and the ever increasing prevalence of depression in the United States, especially among young adults, it is crucial that researchers investigate ways to mitigate both of these undesirable side effects. Current research on the topic fails to directly connect supplementation of vitamin B6 to positive changes in mood in oral contraceptive users. This 12-week long double-blinded, placebo-controlled crossover trial examined the effects of daily supplementation of vitamin B6 as 100 mg of pyridoxine hydrochloride, on mood states in 8 healthy college women (18-25 y) that use combined oral contraceptives. Vitamin status was assessed via plasma pyridoxal 5’-phosphate (PLP). Plasma PLP levels significantly increased by >193% (p=0.003) with daily supplementation of 100 mg B6 over a four week period. Mood changes with supplementation were assessed using the Profile of Mood States (POMS). Although a small improvement in the POMS depression sub score was observed after 4 weeks of vitamin B6 supplementation (14.7%), the changes were insignificant (p>0.05). Furthermore, total mood disturbance scores did not significantly change with either the placebo or supplement periods. While mood states were not improved, a significant decrease in the presence of depressive symptoms as measured by the Beck Depression Inventory was observed after vitamin B6 supplementation, compared to placebo (p=0.047). The results of this study necessitate further investigation into the use of B6 supplementation as a means of reducing negative mood changes in oral contraceptive users. / Dissertation/Thesis / Masters Thesis Nutrition 2020

No description available.

The vitamin B-6 status of 11 white adolescent females living in the Blacksburg/Roanoke, Virginia area was evaluated by dietary intakes, coenzyme stimulation of erythrocyte alanine aminotransferase (F-ALAT) activities, and plasma total vitamin B-6 measured microbiologically. Heights and weights of the group were generally within ranges. The vitamin B-6 intakes of the adolescents were 1.47 ± 0.49 mg/day (mean ± SD). Three subjects, or 27.3%, the same subjects classified as inadequate in status by coenzyme stimulation of E-ALAT, were classified as marginal or inadequate in status using ≤ 25 ng/ml total plasma vitamin B-6 levels as the criterion. The plasma pyridoxal, pyridoxine, pyridoxamine and total B-6 vitamer concentrations of subjects having inadequate E-ALAT values were lower, generally significantly, than those of girls with adequate levels. In the subjects with adequate status, the vitamer found in the largest plasma concentration was pyridoxine. A significant correlation (r = 0.82, p < 0.01) was observed between total plasma vitamin B-6 levels determined microbiologically and coenzyme stimulation values. / Master of Science

The purpose of this study was to compare the nutrient content of a new instant baby food product to jar baby food of similar product formulation. Instant and jar "Vegetable and Beef" and "Bananas" products processed in 1985 and 1987 were analyzed for available lysine, vitamin B-6 and pyridoxyllysine content. The available lysine content of 100 grams of baby food was found to be higher in the instant products, but when adjusted for protein content, available lysine was higher in the jar products. This indicates that drum-drying used for the instant products is more detrimental in regard to lysine availability than retorting. The vitamin B-6 content of the instant products was found to be higher than that of the jar products. However, due to the addition of ingredients with little or no vitamin B-6 content to the jar products, no conclusion about processing effects on vitamin B-6 content can be made. Products processed in 1985 tended to be lower in nutrient content than the products processed in 1987. Pyridoxyllysine, a compound thought to affect vitamin B-6 bioavailability, could not be detected in any of the baby foods, either by amino acid or HPLC analysis. The instant products were found to be at least equal to the jar products with regard to available lysine and vitamin B-6 content. All products also appear to provide sufficient amounts of these nutrients to infants less than one year of age. / Master of Science

The influence of vitamin B-6 intake on vitamin B-6 status and the concentration of B-6 vitamers in milk of 21 white lactating women (21 to 35 years) was examined at 3 to 7 months postpartum. None of the women met the RDA for lactating women of 2.5 mg/day when considering vitamin B-6 intakes from food sources alone. All subjects taking vitamin B-6 supplements had adequate vitamin B-6 status as determined by coenzyme stimulation of erythrocyte alanine aminotransferase activity; all subjects not taking vitamin B-6 supplements had inadequate vitamin B-6 status. Plasma pyridoxal 5-phosphate values were significantly higher for subjects in the supplemented than in the nonsupplemented group. Pyridoxal, pyridoxamine, pyridoxine, and total vitamin B-6 concentrations in milk were higher, sometimes significantly, in the supplemented than in the unsupplemented group as determined by microbiological assay and HPLC. There were significant correlations between data obtained by the microbiological and HPLC analyses for pyridoxal and total vitamin B-6 concentrations. Pyridoxal was the predominant B-6 vitamer found in human milk. Distribution of the B-6 vitamers appeared to stay relatively constant despite vitamin B-6 status. / Master of Science

The growth of many breast cancers is stimulated by the action of the hormone estrogen. Hormonal therapy used to treat these estrogen-dependent breast cancers acts by interfering with the action of estrogen. Current treatments, such as tamoxifen, are not consistently useful due to development of resistance to these drugs. Tamoxifen treatment can also lead to the development of other gynecological cancers, therefore the discovery of novel treatment options for breast cancer is critical. Vitamin B6 is well documented for its role as a modulator of steroid hormones. Pyridoxal phosphate (PLP), the active form of Vitamin B6, may interfere with the action of the estrogen receptor (ER) by blocking the hormone-binding and/or DNA-binding site of the ER. The objective of this study was to examine the effects of Vitamin B6 supplementation on cell proliferation and estrogen-dependent gene expression in breast cancer cells. To accomplish this, estrogen-dependent (MCF-7 and T-47D) and estrogen-independent (BT-20) breast cancer cells were grown in medium supplemented with 0,100, or 300 µM pyridoxal (PL) in the absence or presence of 0.01µM estradiol. Cell counts and [3H]-thymidine incorporation into DNA were assessed in all cell lines. The expression of pS2, an estrogen-sensitive gene, was performed using RNA extracted from MCF-7 cells. PL supplementation was found to significantly decrease total cell numbers and DNA synthesis in both the estrogen-dependent (ER+) and -independent (ER-) breast cancer cells, but did not alter the expression of pS2. These results indicate that PL significantly impairs growth of breast cancer cells and may be exerting its effects via a steroid-independent mechanism. / Master of Science