Amino acid synthesis vitamin

Biotransformations are carried out by either whole cells (microbial, plant, or animal) or by isolated enzymes. Both methods have advantages and disadvantages. In general, multistep transformations, such as hydroxylations of steroids, or the synthesis of amino acids, riboflavin, vitamins, and alkaloids that require the presence of several enzymes and cofactors are carried out by whole cells. Simple one- or two-step transformations, on the other hand, are usually carried out by isolated enzymes. Compared to fermentations, enzymatic reactions have a number of advantages including simple instmmentation reduced side reactions, easy control, and product isolation. 

This series in heterocychc chemistry is being introduced to collectively make available critically and comprehensively reviewed hterature scattered in various journals as papers and review articles. All sorts of heterocyclic compounds originating from synthesis, natural products, marine products, insects, etc. will be covered. Several heterocyclic compounds play a significant role in maintaining life. Blood constituents hemoglobin and purines, as well as pyrimidines, are constituents of nucleic acid (DNA and RNA). Several amino acids, carbohydrates, vitamins, alkaloids, antibiotics, etc. are also heterocyclic compounds that are essential for life. Heterocyclic compounds are widely used in clinical practice as drugs, but all applications of heterocyclic medicines can not be discussed in detail. In addition to such applications, heterocyclic compounds also find several applications in the plastics industry, in photography as sensitizers and developers, and the in dye industry as dyes, etc. 

Vitamin B12 is required by only two enzymes in human metabolism methionine synthetase and L-methylmalonyl-CoA mutase. Methionine synthetase has an absolute requirement for methylcobalamin and catalyzes the conversion of homocysteine to methionine (Fig. 28-5). 5-Methyltetrahydrofolate is converted to tetrahydrofolate (THF) in this reaction. This vitamin B12-catalyzed reaction is the only means by which THF can be regenerated from 5-methyltetrahydrofolate in humans. Therefore, in vitamin B12 deficiency, folic acid can become trapped in the 5-methyltetrahydrofolate form, and THF is then unavailable for conversion to other coenzyme forms required for purine, pyrimidine, and amino acid synthesis (Fig. 28-6). All folate-dependent reactions are impaired in vitamin B12 deficiency, resulting in indistinguishable hematological abnormalities in both folate and vitamin B12 deficiencies. 

Fermentation processes can be a valuable alternative to the conventional chemical synthesis, particularly when the finished product contains specific and complex stereochemistry. Fermentation technology in the industrial synthesis of chemicals started to be used in the first decades of the twentieth century. Industrial production of citric acid by fermentation, achieved by Pfizer in 1923, was an early success in this field. However, it was only with the production of penicillin during the Second World War that the whole sector took off. Today, besides ethanol, the range of products that are produced by fermentation includes antibiotics, organic acids, amino acids, polysaccharides, vitamins, and enzymes. 

Because of the simplicity of swiae and poultry feeds, most feed manufacturers add vitamins (qv) and trace minerals to ensure an adequate supply of essential nutrients. Amino acids (qv) such as methionine [7005-18-7] lysiae [56-87-17, threonine [36676-50-3] and tryptophan [6912-86-3], produced by chemical synthesis or by fermentation (qv), are used to fortify swiae and poultry diets. The use of these supplements to provide the essential amino acids permits diets with lower total cmde proteia coateat. 

Fohc acid is a precursor of several important enzyme cofactors required for the synthesis of nucleic acids (qv) and the metaboHsm of certain amino acids. Fohc acid deficiency results in an inabiUty to produce deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and certain proteins (qv). Megaloblastic anemia is a common symptom of folate deficiency owing to rapid red blood cell turnover and the high metaboHc requirement of hematopoietic tissue. One of the clinical signs of acute folate deficiency includes a red and painhil tongue. Vitamin B 2 folate share a common metaboHc pathway, the methionine synthase reaction. Therefore a differential diagnosis is required to measure foHc acid deficiency because both foHc acid and vitamin B 2 deficiency cause... 

By contrast, the cytoplasmic decarboxylation of dopa to dopamine by the enzyme dopa decarboxylase is about 100 times more rapid (Am 4x 10 " M) than its synthesis and indeed it is difficult to detect endogenous dopa in the CNS. This enzyme, which requires pyridoxal phosphate (vitamin B6) as co-factor, can decarboxylate other amino acids (e.g. tryptophan and tyrosine) and in view of its low substrate specificity is known as a general L-aromatic amino-acid decarboxylase. 

J. Takata, Y. Karube, M. Hanada, K. Matsunaga, Y. Matsushima, T. Sendo, T. Aoyama, Vitamin K Prodrugs 1. Synthesis of Amino Acid Esters of Menahydroquinone-4 and Enzymatic Reconversion to an Active Form , Pharm. Res. 1995, 12, 18-23 J. Takata, Y. Karube, M. Hanada, K. Matsunaga, Y. Matsushima, T. Sendo, R. Oishi, Vitamin K Prodrugs 2. Water-Soluble Prodrugs of Menahydroquinone-4 for Systemic Site-Specific Delivery , Pharm. Res. 1995, 12, 1973- 1979. 

Small methyl groups are important in the stractnre of some small compounds, nucleotides, some bases in DNA mole-cnles and in postranslational modification of amino acids in proteins. The transfer of a single carbon atom is important in the synthesis of purine nncleotides. The componnds involved in the whole process of methyl gronp transfer, and are carbon metolism, are methionine, homocysteine, serine and the vitamins, folic acid and B12. 

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