Folic acid functional

Both sulfonamides and trimethoprim (not a sulfonamide) sequentially interfere with folic acid synthesis by bacteria. Folic acid functions as a coenzyme in the transfer of one-carbon units required for the synthesis of thymidine, purines, and some amino acids and consists of three components a pteridine moiety, PABA, and glutamate (Fig. 44.1). The sulfonamides, as structural analogues, competitively block PABA incorporation sulfonamides inhibit the enzyme dihydropteroate synthase, which is necessary for PABA to be incorporated into dihydropteroic acid, an intermediate compound in the formation of folinic acid. Since the sulfonamides reversibly block the synthesis of folic acid, they are bacteriostatic drugs. Humans cannot synthesize folic acid and must acquire it in the diet thus, the sulfonamides selectively inhibit microbial growth. 

The coenzyme forms of folic acid are derivatives of tetrahydrofolic acid, FH4. See Fig. 7. Folic acid functions as a coenzyme in enzyme reactions which involve the transfer of one-carbon fragments at various levels of... 

We have just seen that folic acid functions as a coenzyme in the synthesis of dXMP It also donates methyl groups in the synthesis of purine bases, so that it is actually quite impor-... 

Folic acid functions in the transfer of one-carbon fragments in a wide variety of biosynthetic and catabolic reactions it is therefore metaboUcaUy closely related to vitamin B12, which also functions in one-carbon transfer. Deficiency of either vitamin has similar clinical effects, and it seems likely that the main effects of vitamin B12 deficiency are exerted by effects on folate metabolism. 

The complexity of the relationship between B12 and folic acid function may extend to an interrelation between their biosyntheses. By analogy with the formation of the purine and pyrimidine rings and riboflavin (see earlier sections), one-carbon fragments may enter into the formation of the pteridine group of folic acid and of the benzimidazole group of Bi2. Further complications are the occurrence of labile one-carbon compounds attached to each the formyl group in folinic acid, and the cyano group in cyanocobalamin. There is also the possibility... 

Licciardi M, Tang Y, BiUingham NC, Armes SP. Synthesis of novel folic acid-functionalized biocompatible block copolymers by atom transfer radical polymerization for gene delivery and encapsulation of hydrophobic drugs. Biomacromolecules 2005 6 1085-96. 

In addition to direct effects of chemical compounds on the fetus, metabolic disturbances in the mother, such as diabetes or hyperthermia, or deficiencies of calories or specific nutrients such as vitamin A, zinc, and folic acid may lead to teratogenesis. Compounds that inhibit placental functions may also induce malformations, e.g., by inhibiting placental circulation. For example, hydroxyurea disrupts the placental circulation and induces malformations. In addition, it also induces DNA damage. 

NAD and NADP and FMN and FAD, respectively. Pantothenic acid is a component of the acyl group carrier coenzyme A. As its pyrophosphate, thiamin participates in decarboxylation of a-keto acids and folic acid and cobamide coenzymes function in one-carbon metabolism. 

The water-soluble vitamins comprise the B complex and vitamin C and function as enzyme cofactors. Fofic acid acts as a carrier of one-carbon units. Deficiency of a single vitamin of the B complex is rare, since poor diets are most often associated with multiple deficiency states. Nevertheless, specific syndromes are characteristic of deficiencies of individual vitamins, eg, beriberi (thiamin) cheilosis, glossitis, seborrhea (riboflavin) pellagra (niacin) peripheral neuritis (pyridoxine) megaloblastic anemia, methyhnalonic aciduria, and pernicious anemia (vitamin Bjj) and megaloblastic anemia (folic acid). Vitamin C deficiency leads to scurvy. 

Pernicious anemia arises when vitamin B,2 deficiency blocks the metabohsm of folic acid, leading to functional folate deficiency. This impairs erythropoiesis, causing immature precursors of erythrocytes to be released into the circulation (megaloblastic anemia). The commonest cause of pernicious anemia is failure of the absorption of vitamin B,2 rather than dietary deficiency. This can be due to failure of intrinsic factor secretion caused by autoimmune disease of parietal cells or to generation of anti-intrinsic factor antibodies. 

With investigations of phytochemicals and functional foods, the outcome measure is generally going to be a biomarker of disease, such as serum cholesterol level as a marker of heart disease risk, or indicators of bone turnover as markers of osteoporosis risk. Alternatively, markers of exposure may also indicate the benefit from a functional food by demonstrating bioavailability, such as increased serum levels of vitamins or carotenoids. Some components will be measurable in both ways. For instance, effects of a folic acid-fortified food could be measured via decrease in plasma homocysteine levels, or increase in red blood cell folate. 

Folic acid and its metabolites called folates are essential to the cell s functions. They act as coenzymes in many biochemical processes. Folate-dependent enzymes are vital to rapidly dividing cell populations, such as the neoplastic or normal-stem cells. Therefore, they are a target for anti-folates in anti-cancer treatment. 

The water-soluble vitamins generally function as cofactors for metabolism enzymes such as those involved in the production of energy from carbohydrates and fats. Their members consist of vitamin C and vitamin B complex which include thiamine, riboflavin (vitamin B2), nicotinic acid, pyridoxine, pantothenic acid, folic acid, cobalamin (vitamin B12), inositol, and biotin. A number of recent publications have demonstrated that vitamin carriers can transport various types of water-soluble vitamins, but the carrier-mediated systems seem negligible for the membrane transport of fat-soluble vitamins such as vitamin A, D, E, and K. 

Thermal ablation using carbon nanotubes is a definite option for use in oncology, especially since nanotubes can be functionalized with targeting modalities like folic acid. Some cancer cell types express large numbers of folic acid receptors on... 

The chemical structure of folate (or folic acid) is shown in Figure 5.8. In humans, folate usually occurs as polyglutamate derivatives. The active form of folate is THF, sometimes shown as FH4) is derived from folate via two reductase reactions. THF functions as a carrier of one-carbon groups in varying oxidation states (Table 5.1). 

The functions of folic acid and vitamin B12 are very closely linked, especially in what is known as one carbon metabolism or methyl group transfer. 

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