Pyridoxine, pyridoxamine 5-phosphate

Clements ]E and Anderson BB (1980) Glntathione reductase activity and pyridoxine (pyridoxamine) phosphate oxidase activity in the red cell. Biochimica etBiophysica Acta 632,159-63. 

The steroids aldosterone, cortisone, cortisol, 11-P-hydroxyandrostenedione, corticosterone, and rostenedione, 11-desoxycorticosterone, 17-hydroxy-progesterone, and progesterone have been performed on Ultrasphere ODS using methanokwater.19 Ranitidine N-[2-[[[5-[(dimethylamino)methyl]-2-furanyl]-methyl]thio]ethyl]-N1-methyl-2-nitro-l,l-ethenediamine has been separated using a p-Bondapak C18 column operated with acetoni-trile methanol water buffered with triethylamine phosphate.117 Pyridoxal-5 -phosphate and other B6 vitamers, including pyridoxamine phosphate, pyri-doxal, pyridoxine, and 4-pyridoxic acid, were separated as bisulfite adducts... 

Identification of pyridoxal phosphate as coenzyme suggested the aldehyde group on pyridoxine might form an intermediate Schiff s base with the donor amino acid. Pyridoxamine phosphate thus formed would in turn donate its NH2 group to the accepting a-ketonic acid, a scheme proposed by Schlenk and Fisher. 15N-labeling experiments and, later, the detection of the Schiff s base by its absorption in UV, confirmed the overall mechanism. Free pyridoxamine phosphate however does not participate in the reaction as originally proposed. Pyridoxal phosphate is invariably the coenzyme form of pyridoxine. 

This enzyme [EC 2.7.1.35] (also known as pyridoxine kinase, pyridoxamine kinase, and vitamin kinase) catalyzes the reaction of ATP with pyridoxal to produce ADP and pyridoxal 5 -phosphate. Pyridoxine, pyridoxamine, and various other derivatives can also act as substrates. 

Pyridoxine (B ) Pyridoxal phosphate Pyridoxamine phosphate Amino acid transformations... 

Vitamin B6 (pyridoxine, pyridoxamine, and pyridoxal) has the active form, pyridoxal phosphate. It functions as a cofactor for enzymes, particularly in amino acid metabolism. Deficiency of this vitamin is rare, but causes glossitis and neuropathy. The deficiency can be induced by isoniazid, which causes sensory neuropathy at high doses. 

The six principal B6 vitamers are widely distributed in foods (102,103). They include pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM), and their 5 -phosphate esters, pyridoxine phosphate (PNP), pyridoxal phosphate (PLP), and pyridoxamine phosphate (PMP) (Fig. 5). The predominate B6 vitamer in animal-based foods is PLP, whereas plant products generally contain PN and PM or their phosphorylated forms. Conjugated vitamers in the form of PN-glycosides have also been isolated from plant-based foods. Pyridoxal is readily converted to PM during cooking and food processing. Total vitamin B6 is the sum of the six principal vitamers inclusion of the conjugated forms depends on the extraction procedure. 

PN = pyridoxine PM = pyridoxamine PL = pyridoxal PNP = pyridoxine phosphate PMP = pyridoxamine phosphate PLP = pyridoxal phosphate PNG = 5 -0-(/8-D-glucopyranosyl)pyri-doxine. 

Wada and Snell (150) have developed a method for the assay of pyridoxine and pyridoxamine phosphate, based on enzymatic oxidation to pyridoxal which is allowed to react with phenylhydrazine. 

Fig. 4. Structures of (a) pyridoxine (vitamin Bg), (b) pyridoxal phosphate and (c) pyridoxamine phosphate.

Three enzymes play an active role in the metabolism of vitamin B6 in human erythrocytes. Pyridoxal kinase uses ATP to phosphorylate pyridoxine, pyri-doxamine, and pyridoxal. Pyridoxamine oxidase oxidizes pyridoxamine-5 -phosphate and pyridoxine-5 -phosphate to pyridoxal-5 -phosphate. The phosphatase activity produces pyridoxal from pyridoxal-5 -phosphate. The assay of the three enzymes required separation of the semicarbazone derivatives of pyridoxal-5 -phosphate and pyridoxal. The mobile phase used by Ubbink and Schnell (1988) contained 2.5% acetonitrile. Detection was by fluorescence. 

Pyridoxine, pyridoxine-5 -phosphate, isopyridoxal (internal standard), ATP, and ADP were separated on a Whatman Partisil-lOSCX column (4.6 mm x 250 mm). The method also resolved pyridoxamine and pyridox-amine-5 -phosphate. The mobile phase was 0.1 M ammonium dihydrogen... 

Figure 9.1. Interconversion of the vitamin Be vitamers. Pyridoxal kinase, EC 2.7.1.38 pyridoxine oxidase, EC 1.1.1.65 pyridoxamine phosphate oxidase, EC 1.4.3.5 and pyridoxal oxidase, EC 1.1.3.12. Relative molecular masses (Mr) pyridoxine, 168.3 (hydrochloride, 205.6) pyridoxal, 167.2 pyridoxamine, 168.3 (dihydrochloride, 241.1) pyridoxal phosphate, 247.1 pyridoxamine phosphate, 248.2 and 4-pyridoxlc acid, 183.2.

Tissue uptake of vitamin Be is again by carrier-mediated diffusion of pyridoxal (and other unphosphorylated vitamers), followed by metabolic trapping by phosphorylation. Circulating pyridoxal and pyridoxamine phosphates are hydrolyzed by extracellular alkaline phosphatase. All tissues have pyridoxine kinase activity, but pyridoxine phosphate oxidase is found mainly in the liver, kidney, and brain. 

Gregory JF 3rd (1980a) Effects of epsilon-pyridoxyllysine and related compounds onliver and brain pyridoxal kinase and liver pyridoxamine (pyridoxine) 5 -phosphate oxidase. Journal of Biological Chemistry 255, 2355-9. 

Vitamin B Three substances are classed under the term pyridoxine or adermine pyridoxol, pyridoxal and pyridoxamine. Pyridoxine was isolated by various study groups in 1938. Its structure was described by Folkers and Kuhn in 1939. Pyridoxal and pyridoxamine were discovered by Snell in 1942. Pyridoxal phosphate and pyridoxamine phosphate are biologically active substances. Intestinal absorption of Bg is dose-dependent and not limited. In alcoholism, a deficiency of vitamin Bg is encountered in 20—30% of cases, whereas the respective percentage is 50—70% in alcoholic cirrhosis. Vitamin Bg is an important coenzyme for transaminases, which transfer amino groups from amino adds to keto acids. In this way, biochemical pathways between the dtiic acid cycle and carbohydrate and amino acid metabolisms are created. (104)... 

TLC of vitamin Be compounds, on various layers in different solvents, was studied. The Rf values of pyri-doxine, pyridoxal, pyridoxamine, pyridoxal ethyl acetate, 4-pyridoxic acid, 4-pyridoxic acid lactone, pyridoxine phosphate, pyridoxal phosphate, and pyridoxamine phosphate were 0.62, 0.68, 0.12, 0.54, 0.91, 0.91, 0.95, 0.95, and 0.86, respectively, by TLC on silica gel HF254 with... 

An early procedure which alfords a quick if inefficient route to toluquinone consists in steam distillation of a mixture of o-toluidine, manganese dioxide, and sulfuric acid. The reagent has been used to oxidize pyridoxine (1) to pyridoxal 2f and to oxidize pyridoxamine phosphate (3) to pyridoxal phosphate (4). ... 

Uptake and Metabolism. The vitamin Bg family consists of pyridoxine, pyridoxal, pyridoxamine, pyridoxine phosphate, pyridoxal phosphate (PLP), and pyridoxamine phosphate (Fig. 8.33). The commercial form is pyridoxine. Pyridoxal phosphate is the coenzyme form. It and pyridoxamine phosphate are from animal tissues. Pyridoxine is from plant tissues. All phosphorylated forms are hydrolyzed in the intestinal tract by phosphatases before being absorbed passively. Conversion to the phosphorylated forms occurs in the liver. Notice that niacin (NAD) and riboflavin (FMN, FAD) are required for interconversion among the vitamin Bq family. The phosphorylated forms are transported to the cells where needed. The major excretory product is 4-pyr-idoxic acid. 

Bi) is converted to thiamine pyrophosphate simply by the addition of pyrophosphate. It is involved in aldehyde group transfer. Niacin (nicotinic acid) is esterified to adenine dinucleotide and its two phosphates to form nicotinamide adenine dinucleotide. Pyridoxine (vitamin B ) is converted to either pyridoxal phosphate or pyridoxamine phosphate before complexing with enzymes. Riboflavin becomes flavin mononucleotide by obtaining one phosphate (riboflavin 5 -phosphate). If it complexes with adenine dinucleotide via a pyrophosphate ester linkage, it becomes flavin adenine dinucleotide. 

Sethi, R., and Haque, W., Pyridoxal-5 -phosphate, pyridoxal, pyridoxine, pyridoxamine, and related analogs for the treatment of cerebrovascular disease, and preparation of compounds, Medicure, Int. Patent Appl. WO 2001072309. 2001 Chem. Abstr, 135, 267243, 2001. 

Pyridoxine (65) Pyridoxal phosphate Pyridoxamine phosphate Carriers of amino and carboxyl groups... 

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