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      Vitamin B 6: A Molecule for Human Health?

      review-article
      * ,
      Molecules
      Molecular Diversity Preservation International
      vitamin B6, PDX, de novo, salvage, health

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          Abstract

          Vitamin B 6 is an intriguing molecule that is involved in a wide range of metabolic, physiological and developmental processes. Based on its water solubility and high reactivity when phosphorylated, it is a suitable co-factor for many biochemical processes. Furthermore the vitamin is a potent antioxidant, rivaling carotenoids or tocopherols in its ability to quench reactive oxygen species. It is therefore not surprising that the vitamin is essential and unquestionably important for the cellular metabolism and well-being of all living organisms. The review briefly summarizes the biosynthetic pathways of vitamin B 6 in pro- and eukaryotes and its diverse roles in enzymatic reactions. Finally, because in recent years the vitamin has often been considered beneficial for human health, the review will also sum up and critically reflect on current knowledge how human health can profit from vitamin B 6.

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          Plasma homocysteine as a risk factor for vascular disease. The European Concerted Action Project.

          Elevated plasma homocysteine is a known risk factor for atherosclerotic vascular disease, but the strength of the relationship and the interaction of plasma homocysteine with other risk factors are unclear. To establish the magnitude of the vascular disease risk associated with an increased plasma homocysteine level and to examine interaction effects between elevated plasma homocysteine level and conventional risk factors. Case-control study. Nineteen centers in 9 European countries. A total of 750 cases of atherosclerotic vascular disease (cardiac, cerebral, and peripheral) and 800 controls of both sexes younger than 60 years. Plasma total homocysteine was measured while subjects were fasting and after a standardized methionine-loading test, which involves the administration of 100 mg of methionine per kilogram and stresses the metabolic pathway responsible for the irreversible degradation of homocysteine. Plasma cobalamin, pyridoxal 5'-phosphate, red blood cell folate, serum cholesterol, smoking, and blood pressure were also measured. The relative risk for vascular disease in the top fifth compared with the bottom four fifths of the control fasting total homocysteine distribution was 2.2 (95% confidence interval, 1.6-2.9). Methionine loading identified an additional 27% of at-risk cases. A dose-response effect was noted between total homocysteine level and risk. The risk was similar to and independent of that of other risk factors, but interaction effects were noted between homocysteine and these risk factors; for both sexes combined, an increased fasting homocysteine level showed a more than multiplicative effect on risk in smokers and in hypertensive subjects. Red blood cell folate, cobalamin, and pyridoxal phosphate, all of which modulate homocysteine metabolism, were inversely related to total homocysteine levels. Compared with nonusers of vitamin supplements, the small number of subjects taking such vitamins appeared to have a substantially lower risk of vascular disease, a proportion of which was attributable to lower plasma homocysteine levels. An increased plasma total homocysteine level confers an independent risk of vascular disease similar to that of smoking or hyperlipidemia. It powerfully increases the risk associated with smoking and hypertension. It is time to undertake randomized controlled trials of the effect of vitamins that reduce plasma homocysteine levels on vascular disease risk.
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            The B6 database: a tool for the description and classification of vitamin B6-dependent enzymatic activities and of the corresponding protein families

            Background - Enzymes that depend on vitamin B6 (and in particular on its metabolically active form, pyridoxal 5'-phosphate, PLP) are of great relevance to biology and medicine, as they catalyze a wide variety of biochemical reactions mainly involving amino acid substrates. Although PLP-dependent enzymes belong to a small number of independent evolutionary lineages, they encompass more than 160 distinct catalytic functions, thus representing a striking example of divergent evolution. The importance and remarkable versatility of these enzymes, as well as the difficulties in their functional classification, create a need for an integrated source of information about them. Description - The B6 database contains documented B6-dependent activities and the relevant protein families, defined as monophyletic groups of sequences possessing the same enzymatic function. One or more families were associated to each of 121 PLP-dependent activities with known sequences. Hidden Markov models (HMMs) were built from family alignments and incorporated in the database. These HMMs can be used for the functional classification of PLP-dependent enzymes in genomic sets of predicted protein sequences. An example of such analyses (a census of human genes coding for PLP-dependent enzymes) is provided here, whereas many more are accessible through the database itself. Conclusion - The B6 database is a curated repository of biochemical and molecular information about an important group of enzymes. This information is logically organized and available for computational analyses, providing a key resource for the identification, classification and comparative analysis of B6-dependent enzymes.
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              Vitamin B6: A Long Known Compound of Surprising Complexity

              In recent years vitamin B6 has become a focus of research describing the compound’s critical function in cellular metabolism and stress response. For many years the sole function of vitamin B6 was considered to be that of an enzymatic cofactor. However, recently it became clear that it is also a potent antioxidant that effectively quenches reactive oxygen species and is thus of high importance for cellular well-being. In view of the recent findings, the current review takes a look back and summarizes the discovery of vitamin B6 and the elucidation of its structure and biosynthetic pathways. It provides a detailed overview on vitamin B6 both as a cofactor and a protective compound. Besides these general characteristics of the vitamin, the review also outlines the current literature on vitamin B6 derivatives and elaborates on recent findings that provide new insights into transport and catabolism of the compound and on its impact on human health.
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                Author and article information

                Journal
                Molecules
                Molecules
                molecules
                Molecules
                Molecular Diversity Preservation International
                1420-3049
                20 January 2010
                January 2010
                : 15
                : 1
                : 442-459
                Affiliations
                Washington State University, Abelson 435, P.O. Box 66224, Pullman, WA, USA
                Author notes
                [* ] Author to whom correspondence should be addressed; E-Mail: hellmann@ 123456wsu.edu .
                Article
                molecules-15-00442
                10.3390/molecules15010442
                6257116
                20110903
                fdb332e4-493f-42a1-8dbc-107ce36667d4
                © 2010 by the authors;

                licensee Molecular Diversity Preservation International, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

                History
                : 05 November 2009
                : 16 January 2010
                : 20 January 2010
                Categories
                Review

                vitamin b6,pdx,de novo,salvage,health
                vitamin b6, pdx, de novo, salvage, health

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