Pyridoxine vitamin pyridoxamine

Vitamin B6. Figure 1 Structure of pyridoxin, pyridoxal, pyridoxamine, and the coenzymes pyridoxal-5 -phosphate and pyridoxamine-5Y-phosphate. 

Six compounds have vitamin Bg activity (Figure 45-12) pyridoxine, pyridoxal, pyridoxamine, and their b -phosphates. The active coenzyme is pyridoxal 5 -phos-phate. Approximately 80% of the body s total vitamin Bg is present as pyridoxal phosphate in muscle, mostly associated with glycogen phosphorylase. This is not available in Bg deficiency but is released in starvation, when glycogen reserves become depleted, and is then available, especially in liver and kidney, to meet increased requirement for gluconeogenesis from amino acids. 

Vitamin Ba (pyridoxine, pyridoxal, pyridoxamine) like nicotinic acid is a pyridine derivative. Its phosphorylated form is the coenzyme in enzymes that decarboxylate amino acids, e.g., tyrosine, arginine, glycine, glutamic acid, and dihydroxyphenylalanine. Vitamin B participates as coenzyme in various transaminations. It also functions in the conversion of tryptophan to nicotinic acid and amide. It is generally concerned with protein metabolism, e.g., the vitamin B8 requirement is increased in rats during increased protein intake. Vitamin B6 is also involved in the formation of unsaturated fatty acids. 

Vitamin Bg a family of molecules having vitamin Be activity these include pyridoxal, pyridoxine, and pyridoxamine precursors to the coenzyme pyridoxal phosphate. 

We have just noted the role that pyridoxal phosphate plays as a coenzyme (cofactor) in transamination reactions (see section 15.6). Pyridoxal 5 -phosphate (PLP) is crucial to a number of biochemical reactions. PLP, together with a number of closely related materials that are readily converted into PLP, e.g. pyridoxal, pyridoxine and pyridoxamine, are collectively known as vitamin Bg, which is essential for good health. 

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 (vitamin Be) is essential for protein metabolism and plays an important role in hemoglobin production. Pyridoxamine and pyri-doxal also possess vitamin Be activity. Sources of... 

Pyridoxamine pyruvate aminotransferase, stereochemistry of 748 Pyridoxine (vitamin B6) 305s, 738... 

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

All three forms of vitamin B6 [pyridoxal, pyridoxine, and pyridoxamine] are phosphorylated by a single kinase that uses ATP as the phosphate donor. This assay describes the use of pyridoxamine as the substrate. 

Pyridoxine (pyridoxol), pyridoxamine, and pyridoxal are the three natural forms of vitamin Bg. They are converted to pyridoxal phosphate, which is required for the synthesis, catabohsm, and interconversion of amino acids. 

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. 

Pytidoaal (vitamin B ) Pyrldoxal phosphate Amino group and decarboxylation (i) Pyridoxine (ii) Pyridoxamine or pyridoxal fiii) Pyridoxal phosphate PtnlcUlium spent mycelium Yeast Rice polishings Cere Wheat seeds Maize seeds Cornsteep liquor Cottonseed flour... 

Pyridoxine (Vitamin Bg) IX), pyridoxal (A), and pyridoxamine XI), which are normally available in the diet, must be converted in vivo to the active co-enzyme pyridoxal phosphate XII) as shown in Figure 4.1. Inhibition of pyridoxal phosphate production in vivo results in reduced activity of pyridoxal-dependent enzymes. The extent of the inhibition may vary from one enzyme system to another, depending on the affinities of the apo-cnzymes for the co-enzyme. 

Description. There are six forms of vitamin Bgi pyridoxal (PL), pyridoxine (PN), pyridoxamine (PM), and their phosphate derivatives pyridoxal 5 -phosphate (PLP), pyridoxine 5 -phosphate (PNP), and pyridoxamine 5 -phosphate (PMP). PLP is the active coenzyme form and has the most importance in human metabolism. ... 

Nomenclature. Pyridoxine (vitamin Bg) group name for pyridoxine (pyridoxol), pyridoxal, pyridoxamine and the 5 -phosphorylated derivatives of these compounds. 

TLC of vitamin Bg compounds, on various layers in different solvents, was studied. The Rf values of pyridoxine, 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 0.2% NH4OH in water as solvent. When adsorbents containing fluorescent indicators are used, all forms and derivatives of vitamin Bg can be detected... 

Studies based on the use of an antivitamin, deoxypyri-doxine, have established that the daily requirement of the vitamin ranges between 1 and 2 mg in the human adult. A normal diet has been reported to provide 1-1.5 mg daily of the vitamin. Food appears to be the only source of the vitamin because most of the vitamin produced by the bacterial flora of the intestine is excreted in the feces, possibly after oxidation to 4-pyridoxic acid. The ingested vitamin is rapidly and completely absorbed, but the exact site of the absorption is not known. Although both pyridoxine and pyridoxamine can be excreted as such and are therefore normal constituents of human urine, part of the vitamin is oxidized to the 4-pyridoxic acid before excretion in the urine. Mammalian tissues contain at least two enzymes capable of oxidizing pyridoxine. Both enzymes seem to be flavoproteins. One attacks pyridoxine, the other attacks pyridoxine phosphate. The pyridoxine phosphate oxidase of liver has been purified 65 times. Although the enzyme was shown to act on pyridoxamine phosphate, pyridoxamine phosphate was oxidized only when the pH of the incubation mixture was raised to 10. Pyridoxine phosphate oxidase has no effect on pyridoxamine phosphate at physiological pH. 

Vitamin Be extraction and analysis is complicated by several factors including its occurrence as six vitamers of differing structures. The total vitamin Bg content of food has traditionally been determined by extraction at elevated temperatures (autoclaving) in the presence of mineral acids, followed by enzymatic hydrolysis (Rabinowitz and Snell 1947) with phosphatases and glucosidases to ensure complete release and conversion of all Bg vitamers into pyridoxine (PN), pyridoxamine (PM) and pyridoxal (PL) (AOAC 2006). 

Vitamin Bg in its various forms has antioxidant properties that compare favorably with those of the well-established antioxidant vitamins such as vitamin C and the tocopherols. Pyridoxine and pyridoxamine inhibit superoxide radicals and prevent lipid peroxidation, protein glycosylation, and Na+,K+-ATPase activity in high glucose-treated erythrocytes and hydrogen peroxide-treated monocytes (2) and endothelial cells (3). In bovine endothelial cells, treatment with homocysteine and copper increased extracellular hydrogen peroxide levels. Treatment with pyridoxal or EDTA prevented such increases and enhanced the viability of the cells by supporting apoptosis. 

Pyridoxine (vitamin Be) was first recognized as an essential factor in animal nutrition. Later it was found to have growth-promoting ability for various strains of bacteria, yeast, molds, fungi, and plants. Snell, in a series of studies with bacteria, noted variations in response to certain natural extracts as source of Be among several bacteria. Out of this work came the appreciation that vitamin Be existed in several different forms to which various test organisms responded differently. The vitamin Be complex is now known to consist of the following compounds pyridoxine, pyridoxal, pyridoxamine, and the phosphorylated forms of the two latter substances. 

Figure 6 Chromatogram of water-soluble vitamins from standard solution. Ion pair chromatography with a reversed-phase Cig column (Tracer Spherisorb ODS 2, 250 X 4.6 mm i.d., 5 pm) UV detection at different wavelengths mobile phase (1 mL/min) contained octanesulfonic acid (5 mM), triethylamine (0.5%), glacial acetic acid (2.4%), and methanol (15%) at pH 3.6. Peak identities (1) nicotinamide (2) pyridoxal (3) pyridoxine (4) pyridoxamine (5) folic acid (6) riboflavin (7) cyanocobalamin (8) thiamin. (From Ref. 94.)...

The simultaneous determination of the B vitamins, thiamine, riboflavin, pyridoxal, pyridoxine, and pyridoxamine in a pharmaceutical product using CZE was described by Huopalahti and Sunell (90). Hydrochlorid acid was used for the extraction of the vitamins from the multivitamin-multimineral tablet. The applied potential was 6.0 kV, and a 75-p.m fused-silica capillary tubing was used. The electrolyte used was a 20-mM sodium phosphate buffer pH 9.0. A clear separation of standards as well as of the pharmaceutical sample is shown in Figure 14. This method appears to be a fast and simple technique for the simultaneous determination of water-soluble vitamins in pharmaceutical products, where the... 

At the present time, 9 fractions of the vitamin B complex are generally recognized, and others are postulated. Those discussed in this book (alphabetically under their name designations) are biotin, choline, folacin (folic acid), niacin (nicotinic acid nicotinamide), pantothenic acid (vitamin B-3), riboflavin (vitamin B-21), thiamin (vitamin B-1), vitamin B-6 (pyridoxine, pyridoxal pyridoxamine), and vitamin B-12 (cobalamins). 

There are several metabolic interrelationships between riboflavin and vitamin Bg. The conversion of pyridoxine or pyridoxamine phosphates to pyri-doxal phosphate is catalyzed by a flavoenzyme (pyri-doxaminephosphate oxidase EC 1.4.3.5), so that a deficiency of riboflavin may, at certain key sites, result in a secondary deficiency in Bg-dependent pathways. More evidence is needed to clarify the extent and importance of these interactions. 

The related compounds pyridoxamine and pyridoxal, in which the CH2OH group in the 4-position is replaced by CH2NH2 and CHO respectively, also possess vitamin activity and for certain bacteria are much more active than pyridoxine. 

Pyridoxal hydrochloride, pyridoxamine hydrochloride and pyridoxine hydrochloride (vitamin Bg) see entries in Chapter 6. 

Goldberger and Lillie in 1926 found that rats fed certain nutritionally deficient diets developed dermatitis acrodynia, a skin disorder characterized by edema and lesions of the ears, paws, nose, and tail. Szent-Gyorgyi later found that a factor he had isolated prevented these skin lesions in the rat. He proposed the name vitamin Bg for his factor. Pyridoxine, a form of this vitamin found in plants (and the form of Bg sold commercially), was isolated in 1938 by three research groups working independendy. Pyridoxal and pyridoxamine, the forms that predominate in animals, were... 

In general, pyridoxamine and pyridoxin are more stable than pyridoxal. All vitamers are relatively heat-stable in acid media, but heat labile in alkaline media. All forms of vitamin B6 are destroyed by UV light in both neutral and alkaline solution. The majority of vitamin B6 in the human body is stored in the form of pyridoxal phosphate in the muscle, bound to glycogen phos-phorylase. 

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