Pyridoxine/pyridoxal/pyridoxamine deficiency

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. 

The vitamin Be group of coenzymes consists of pyridoxine, pyridoxal, and pyridoxamine and their metabolically active phosphorylated forms. They are striking for the variety of enzymic reactions in which they are important, and many amino acid transformations, including various transaminations and decarboxylations, are vitamin B dependent. Compounds with vitamin B activity are apparently not stored in the body in large amounts, and biochemical evidence of B deficiency can develop quickly if intake is inadequate (S4). 

Vitamin B is a general term to refer to pyridoxine, pyridoxal, and pyridoxamine. Experimental animals deficient in vitamin B< show a dermatitis, and sometimes a microcytic anemia, hemosiderosis, fatty livers, and demyelinization of nerves. Somewhat similar findings have been reported in man (Nutrition Reviews, 1954a). Vitamin B is synthesized to some extent in man. Some intestinal bacteria may S3mthesize it, while others can produce an antivitamin that would complicate any estimation of requirements, especially requirements to be met by the diet. 

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... 

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. 

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)... 

Vitamers are chemically similar substances that have a qualitatively similar vitamin activity. Thus, vitamin D refers to ergocalciferol (Da) and cholecalciferol (D3) and sometimes to their 25-hydroxy- and 1,25-dihydroxy derivatives (Chapter 37). Similarly, pyridoxine (pyri-doxol), pyridoxal, and pyridoxamine are vitamin Be vitamers, riboflavin is the active form of vitamin Ba and cobalamin is vitamin Bia- The members of a particular vitamin family are functionally interchangeable and protect against deficiency symptoms for that vitamin. A vitamin and its corresponding deficiency disease are related as follows ... 

Pyridoxol 210 (pyridoxine, 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridine, vitamin B6) was formerly known as adermine (Kuhn 1938) because vitamin B5 deficiency causes skin diseases in animals. Pyridoxal (211, R = CHO) and pyridoxamine (211, R = CH2NH2) also belong to the vitamin B group. Pyridoxal phosphate 212 is a coenzyme for many of the enzymes involved in the metabolism of amino acids. Nicotinamide adenine dinucleotide 213 (NAD , reduced form NADH) is a component of oxidoreductases (for its action see p 293, synthesis see p 131). 

Pyridoxal Phosphate, Codecarboxylase. An independent approach to the nature of the amino acid decarboxylases was made by Gunsalus, Umbreit, and collaborators. They found that the production of tyrosine decarboxylase by Streptococcus faecalis depended on the vitamin, pyri-doxine. In the absence of pyridoxine the cells grew but had little decarboxylase. However, addition of the vitamin permitted deficient cells to decarboxylate tyrosine, and dried cells exhibited active enzyme in the presence of pyridoxal (a derivative of pyridoxine) and ATP, implying the formation of an active cofactor from these substances. Pyridoxal is a more active growth factor for a strain of Streptococcus faecalis than pyridoxine both synthetic pyridoxal and pyridoxamine exhibit 5000 to 9000 times the activity of the hydroxy compound. ... 

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