Pyridoxal Pyridoxamine

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

Be Pyridoxine, pyridoxal, pyridoxamine Coenzyme in transamination and decarboxylation of amino acids and glycogen phosphorylase role in steroid hormone action Disorders of amino acid metabolism, convulsions... 

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. 

The usable range for T. pyriformis is from 0.3-300 mug/ml. The organism utilizes pyridoxal, pyridoxamine pyridoxine, and pyridoxal-5-phosphate. Pyridoxamine + pyridoxal yielded the best growth approximately 120 times more pyridoxine is required to yield the same growth as pyridoxamine (Fig. 4). As with nicotinic acid and its amide, when these compounds are added together in the same concentration, the increment of growth is less than the sum of the individual increments. Upon an intramuscular load dose of 100 mg of pyridoxine, peak vitamin Bs levels are reached 2 hours after injection. The curves for 4 normal individuals are illustrated in Fig. 5. 

This review will explore some of the issues involved in developing novel peptides and proteins that integrate coenzyme functionaUty and highlights recent progress in this area. For the sake of depth, this review focuses specifically on the pyridoxal/pyridoxamine system, thiamine, and selected redox active coenzymes. These coenzymes and information on the transformations that they mediate are summarized in Fig. 1. 

Fig. 2. Catalytic cycle of pyridoxal/pyridoxamine-dependent transamination...

Pyridoxal-5 -phosphate is the coenzyme form of vitamin B6, and has the structure shown in figure 10.3. The name vitamin B6 is applied to any of a group of related compounds lacking the phosphoryl group, including pyridoxal, pyridoxamine, and pyridoxine. 

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. 

The phosphorylated vitamers are dephosphorylated by membrane-bound alkaline phosphatase in the intestinal mucosa pyridoxal, pyridoxamine, and pyridoxine are all absorbed rapidly by carrier-mediated diffusion. Intestinal mucosal cells have pyridoxine kinase and pyridoxine phosphate oxidase (see Figure 9.1), so that there is net accumulation of pyridoxal phosphate by metabolic trapping. Much of the ingested pyridoxine is released into the portal circulation as pyridoxal, after dephosphorylation at the serosal surface. 

Kelsay J, Baysal A, and Linkswiler H (1968a) Effect of vitamin Bg depletion on the pyridoxal, pyridoxamine and pyridoxine content of the blood and urine of men. Journal of Nutrition 94, 490-4. 

Pyridoxal phosphate PP Amino group Pyridoxal (Pyridoxamine)... 

Pyridoxal, pyridoxamine and pyfidoxine are collectively known as vitamin-B6. All three compounds are efficiently converted to the biologically active form of vitamin-B6, pyridoxal phosphate. The ATP requiring enzyme, pyridoxal kinase, catalyzes this conversion. 

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... 

Chemical Name Pyridoxine Chemical Abstracts Services Registry Numbers CAS 58-56-0 CAS 65-23-6 Synonyms Vitamin Pyridoxal Pyridoxamine Adermine hydrochloride 3,4-Pyridinedimethanol 5-Hydroxy-6-methyl hydrochloride Chemical/Pharmaceutical/Other Class Water-soluble vitamin... 

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. 

The B0 vitamins (pyridoxal, pyridoxamine, and pyridoxine and their phos-phorylated forms, which are the coenzymes) are involved in the transfer of amino groups from one molecule to another, an important step in the biosynthesis of amino acids (Figure 7.20). In the reaction, the amino group is transferred from the donor to the coenzyme and then from the coenzyme to the ultimate acceptor (Figure 7.21). 

Biological assay of pyridoxal, pyridoxamine and pyridoxine. J. biol. Chem. 165, 55 (1946). 

Pyridoxines. An obsolete collective name for pyridine derivatives with vitamin B5 activity. According to lUPAC rule M-7 the name P. should only be used for 4,5-bis(hydroxymethyl)-2-methyl-3-pyridinol and its esters and ethers. The name vitamin B5 is recommended as collective name for P., pyridoxal, pyridoxamine derivatives, etc.. 

An investigation has been conducted by Mpller (1953) in which measurements were made of the contents of pyridoxal, pyridoxamine, and phos-phorylated vitamin Be derivatives in tissue samples (liver, heart, kidney, spleen) obtained from 10 subjects ranging in age from 0 to 76 years. No significant variations with age in the concentrations of these compounds were encountered essentially similar values were observed for samples from newborn children and from adult individuals. 

The fluorimetric determination of vitamin Bg compounds (pyridoxine, pyridoxamine, pyridoxal, pyridoxamine 5 -phosphate, pyridoxal 5 -phosphate, and 4-pyridoxic acid) in foods by measurement of their native fluorescence entails a prior LC isolation. Some of these determinations involve postcolumn derivatization with sodium bisulfite in a phosphate... 

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

Pyridoxine, pyridoxal, pyridoxamine, pyridoxal phosphate, pyridoxamine phosphate, and 4-pyridoxic acid were baseline resolved and detection limits of -C1 pmol were obtained on a C g column (A = 328nm, ex 393 nm, em) using a 0/100 -> 100/0 (at lOmin hold lOmin) IPA/water (33mM phosphate buffer pH 2.2 with lOmM octanesulfonic acid) gradient [327]. Excellent quantitative results from spinal fluid samples were also obtained. 

Pyridoxine, pyridoxal, pyridoxamine, pyridoxal phosphate, and pyridoxamine phosphate were extracted from cooked sausage and separated on a 35°C deactivated base C 8 column (A = 290nm, ex 395 nm, em) using a 99/1 water (50 mM KH2PO4 buffer at pH 3.2)/acetonitrile mobile phase [1585]. Very good peak shapes and resolution were achieved and elution was complete in 4 min. Linear ranges were reported as 10-500 pg injected and detection limits of 0.02-0.5 mg/100 g sample were cited (analyte dependent). 

Most of the vitamin Be in natural materials is present as phosphorylated derivatives of compounds I-III. Pyridoxal-5-phosphate (IV, Fig. i) was discovered in 1944 by Gale and Epps as an unidentified compound required for enzymatic decarboxylation of amino acids Gunsalus and co-workers subsequently showed it to be a phosphorylated pyridoxal -. Pyridoxamine-5-phosphate (V, Fig. i) was discovered by Rabinowitz and Snell by virtue of its differential activity in promoting growth of certain lactic acid bacteria. It is probable that pyridoxine-5-phosphate also occurs naturally, since it is both formed and oxidized to pyridoxal-5-phosphate by tissue enzymesi -. An unidentified conjugate of pyridoxine also occurs in cereal grains - . 

---