Vitamin derivatives

Examples of coenzymes vitamin-derived nucleotides for example adenosine phosphates ATP, ADP, AMP nicotinamide derivatives NAD+, NADH, NADP+, NADPH flavin derivatives FAD, FADH2 coenzyme A (abbreviated to CoA, CoASH or CoA-SH). 

It is a synthetic vitamin derivative effective in the treatment of plaque type psoriasis vulgaris. Adverse effects include itching and mild irritation. 

Inadequate saturation of enzymes with (vitamin-derived) coenzymes. This can be tested for three vitamins, using red blood cell enzymes thiamin (Section 6.5.3), riboflavin (Section 7.5.2), and vitamin Be (Section 9.5.3). 

Multivitamin products for parenteral administration are available in a variety of compositions from different manufacturers. As different formulations are available generally, valid stability information cannot be provided. Stability data obtained on vitamins, derived from studies of a single vitamin, cannot be accurately extrapolated to all multivitamin preparations because of possible vitamin, preservative, and excipient interactions. 

The catalysts in biological systems are enzymes, and nearly all enzymes are proteins. Enzymes are highly specific and have great catalytic power. They can enhance reaction rates by factors of 10 or more. Many enzymes require cofactors for activity. Such cofactors can be metal ions or small, vitamin-derived organic molecules called coenzymes. 

Quinones and, in particular, naphthoquinone derivatives are industrially valuable products for further processing and for direct use due to their pronounced bioactivity [la,b], 2-Methyl-1,4-naphthoquinone, vitamin K3 ( menadione ), is the basis of the vitamin K group (coagulation vitamins). The skeleton of 2-methyl-1,4-naphthoquinone is common to all fat-soluble K vitamins. Derivatives of vitamin K promote the formation of prothrombin and other blood coagulation factors. They are used on an industrial scale as supplement in animal feed, but are also employed in the treatment of Melaena neonatorum in newborn babies. Trimethyl-p-benzoquinone is a key compound for the synthesis of vitamin E, active as antioxidant agent. As an example, the current method of the production of trimethyl-p-benzoquinone on an industrial scale is p-sulfo-nation of 2,3,6-trimethylphenol followed by stoichiometric oxidation using Mn02 [Ic]. 

Chemical/Pharmaceutical/Other Class Pat-soluble vitamin, derived from retinol... 

Disposable transport-facilitating moieties are also used to enhance the absorption of the water-soluble vitamins used as food additives, such as thiamine, ascorbic acid, and riboflavine. The vitamin derivatives obtained are poorly water-soluble and therefore are less extracted during the preparation of the food, which also gives some protection against oxidative decomposition. The increased lipophilicity enhances absorption from the intestinal tract (Fig. 32)151 155>. 

Vitamin D is a fat soluble vitamin derived from cholesterol. In the human epidermis (skin), sunlight spontaneously oxidizes cholesterol to 7-dehydrocholesterol (Fig. 10.10a). The 7-dehydrocholesterol leaks into the blood where it isomerizes to cholecalciferol (vitamin D3, Fig. 10.10b and c). Cholecalciferol is enzymatically hydroxylated at C25 in the liver (25-cholecalciferol) and then passes to the kidney where another enzyme is activated by parathyroid hormone to hydroxylate it at Cl, forming calcitriol (Fig. lO.lOd). The kidney hydroxylase is sensitive to feedback inhibition. As the amount of calcitriol increases, it binds to the hydroxylase and alters the specificity of the kidney enzyme. Additional 25-cholecal-ciferol is hydroxylated to 24,25-dihydroxycholecalciferol (inactive calcitriol) instead of 1,25 dihydroxycholecalciferol (calcitriol). Other vitamin D derivatives that can be converted to calcitriol are obtained enzymatically from cholesterol in other vertebrates. The most common of these are vitamin D3 (lamisterol) and D2 (ergosterol) from cold-water fish such as cod, where their presence keeps membranes fluid at low body temperatures 10-20°C. 

The answer is a. (Murray, pp 627-661. Scriver, pp 3897-3964. Sack, pp 121-138. Wilson, pp 287-320.) Vitamins A, D, E, and K are all fat-soluble. The physical characteristics of fat-soluble vitamins derive from the hydrophobic nature of the aliphatic chains composing them. The other vitamins listed are water-soluble, efficiently administered orally, and rapidly absorbed from the intestine. Fat-soluble vitamins must be administered intramuscularly or as oral emulsions (mixtures of oil and water). In intestinal disorders such as chronic diarrhea or malabsorption due to deficient digestive enzymes, fat-soluble vitamins are poorly absorbed and can become deficient. Supplementation of fat-soluble vitamins is thus routine in disorders like cystic fibrosis (219700), a cause of respiratory and intestinal disease that is the likely diagnosis in this child. 

Folic acid does this by improving the fit between an enzyme and its cofactor. The enzyme in this case is known shorthand as MTHFR, and the cofactor, a molecule called FAD, is also vitamin-derived (from vitamin B2) and is essential for converting homocysteine to methionine. Martha Ludwig and Rowena Matthews, both of the University of Michigan Medical School in Ann Arbor, determined that by locking FAD onto MTHFR, folic acid performs this protective role in the body. 

The ratio of methylcobalamin to total vitamin derivatives of extractable B12 has been determined in liver from mice who were subjected to different types of injury (mechanical trauma, bums, and ionizing radiation) inflicted separately or in various combinations. A decrease in methylcobalamin was observed paralleling the severity of the damage. There may thus be a decreased synthesis of methycobalamin or an increased catabolism or leakage from the liver—or combination of these causes. The method used did not determine the nonextractable cobalamin, so that a disappearance into a nonextractable form could have been the cause (L9). 

Vitamin A is a fat soluble vitamin derived from carotene. The alcohol form of vitamin A, retinol, is the storage form in the body. The aldehyde form, retinal, has a role in vision. The acid form, retinoic acid, functions in embryonic development. Vitamin A acts to some extent in the body as an antioxidant, protecting against oxidative damage. 

Some enzymes require cofactors, which are amino acids, vitamin derivatives, or metals (minerals) that bound as co-substrates or remain attached through multiple catalytic cycles. 

As with transamination reactions, the first step is the formation of a Schijfbase between the amino acid and the vitamin derivative, pyridoxal phosphate ... 

We have already mentioned two vitamin-derived cofactors involved in the PDH reaction (CoA and NAD+), but in addition three others are involved - thiamine pyrophosphate (TPP) from vitamin B1, FAD from riboflavin (vitamin B2) and lipoic acid, so the PDH step depends on flve different vitamins and would fail if any of them were missing. 

The enzymatic conversion of pyruvic acid to acetyl CoA normally involves five vitamin-derived cofactors. If two if these five were unavailable over a prolonged period would you expect... 

Figure A6.1 Structures of three of the vitamin-derived cofactors. NAD, like several other cofactors, has a handle consisting of adenine (blue) and ribose phosphate (black), but the actual chemistry of oxidation and reduction is done by the nicotinamide (red), which is derived from the vitamin nicotinic add or niacin. Note the positive charge on the ring nitrogen in the oxidised form, NAD+, which is shown here. Pyridoxal phosphate, derived from vitamin carries out its chemical contribution via the aldehyde group (mauve). Biotin likewise contributes its own characteristic chemistry, with the nitrogen atom, shown in blue, readily able to pick up CO2 as a carboxyl group.

CoA Coenzyme A, a B-vitamin-derived cofactor essential for fatty acid metabolism, pyruvate oxidation, TCA cycle, etc. 

Fig. 3 An example of artificial holoenzyme formed with the octopus cyclophane (6) and the hydrophobic vitamin derivative (7).

Preparation and characterization of liposomes formed with natural phospholipids were well established. However, in using liposomes for simulation of enzymatic functions, especially in acid-base catalysis, difficulties would be encountered due to their chemicai and morphological instabilities. Thus, bilayer membranes composed of synthetic amphiphiles are more favorable candidates for enzyme mimics. For example, artificial vitamin Bg-dependent enzymes were constructed from catalytic bilayer membranes in combination with a bilayer-forming peptide lipid (10), a hydrophobic vitamin derivative (11), and metal ions (Fig. 5). The catalyst acts as an artificial aminotransferase, showing marked substrate specificity, high enantioselectivity, and turnover behavior for the transamination of a-amino acid with a-keto acids. In addition, the reaction fields provided by the catalytic bilayer membranes are suitable to establish multienzyme systems through functional ahgnments of artificial enzymes and natural ones in a sequential manner. 

Figure 3.8. Structures of vitamins or vitamin-derived molecules that function in oxidation-reduction reactions. The oxidation of these redox groups in the inner mitochondricil membrane contributes to the electron transport chain that carries electrons from the oxidation of glucose to oxygen and in the process pumps protons from one side to the other of the inner mitochondrial membrane (see Chapter 8 for details). The proton gradient thus formed is used to phosphorylate ADP to form 32 of the 36 ATPs resulting from the oxidation of one glucose molecule to six CO2 and six H2O molecules. A Vitamin B3, also called niacin or nicotinic acid, becomes converted to the amide (nicotinamide) and dressed up with a ribose sugar. Then, in a manner like that of riboflavin in B becomes phosphorylated to form nicotinamide mononucleotide (NMN) or further reacted with the addition of adenosine monophosphate (AMP) to form nicotinamide adenine dinucleotide (NAD). B Vitamin B2, also known as riboflavin, is shown converted to the forms involved in redox reactions such as those of the electron transport chain. (From Biochemistry, Second Edition, D. Voet and J. Voet, Copyright 1995, John Wiley Sons, New York. Reprinted with permission of John Wiley Sons, Inc.)...

Uses Antistat in cosmetics vitamin deriv. for hair care, skin care, lip care, massage and skin care oils nutrient, humectant in pharmaceuticals promotes healing Use Level 1-5%... 

Potassium ascorbate vitamin D source, enriched farina Yeast, dried irradiated vitamin D, pharmaceuticals Cod liver oil vitamin deriv., hair care Panthenyl triacetate vitamin deriv., lip care Panthenyl triacetate vitamin deriv., massage oils Panthenyl triacetate vitamin deriv., skin care Panthenyl triacetate vitamin deriv., skin care oils Panthenyl triacetate vitamin E precursor synthesis N-Methyl-2-pyrrolidone vitamin E source Wheat (Triticum vulgare) germ oil vitamin E source, food... 

The oxidation of thiols has biological relevance too. Thiol groups are present in the amino acid cysteine and the tripeptide glutathione, which are catalytically oxidized by vitamin derivatives [29,30]. 

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