Dinucleotide liberation

XOD is one of the most complex flavoproteins and is composed of two identical and catalytically independent subunits each subunit contains one molybdenium center, two iron sulfur centers, and flavine adenine dinucleotide. The enzyme activity is due to a complicated interaction of FAD, molybdenium, iron, and labile sulfur moieties at or near the active site [260], It can be used to detect xanthine and hypoxanthine by immobilizing xanthine oxidase on a glassy carbon paste electrode [261], The elements are based on the chronoamperometric monitoring of the current that occurs due to the oxidation of the hydrogen peroxide which liberates during the enzymatic reaction. The biosensor showed linear dependence in the concentration range between 5.0 X 10 7 and 4.0 X 10-5M for xanthine and 2.0 X 10 5 and 8.0 X 10 5M for hypoxanthine, respectively. The detection limit values were estimated as 1.0 X 10 7 M for xanthine and 5.3 X 10-6M for hypoxanthine, respectively. Li used DNA to embed xanthine oxidase and obtained the electrochemical response of FAD and molybdenum center of xanthine oxidase [262], Moreover, the enzyme keeps its native catalytic activity to hypoxanthine in the DNA film. So the biosensor for hypoxanthine can be based on... 

The liberated nicotinamide-adenine-dinucleotide hydrogenase (NADH) has an absorption maxima at 340 nm, whereas lactic acid. NAD+ and pyruvic acid do not absorb at all at this wavelenath. 

Glutamate dehydrogenase, the enzyme responsible for the liberation of ammonia from amino acids, occurs in two forms one (cytosolic) is nicotinamide adenine dinucleotide (NAD+) dependent whilst the other (mitochondrial) requires NADP+ as coenzyme. 

Riboflavin is the redox component of flavin adenine dinucleotide FAD. It is derived from FAD by hydrolysis of a phosphate ester link. The fully oxidised form of FAD is involved in many dehydrogenaze reactions during which it is converted to the fully reduced form. The fully oxidised state is restored either by another redox enzyme or by interaction with oxygen and hydrogen peroxide is liberated. The one-electron reduced, semiquinone form of FAD, is involved in some electron transfer steps. 

In addition, the DNPH (2,4-dinitrophenylhydrazine) [38] and NADH (dihydronicotinamide adenine dinucleotide) [36] studies with purified Iso-4 provided the evidence that the 70 Da moiety was a pyruvate derivative (C3H2O2). In the DNPH study, treatment of Iso-4 with acid and 2,4-dinitrophenylhydrazine produced the 2,4-dinitrophenylhydrazone of the pyruvic acid liberated from Iso-4. In the NADH study, the amount of NAD+... 

It would be of interest to halt the hydrolysis when liberation of guanosine and adenosine approaches a maximum, and determine whether the pyrimidine nucleotides are present as a dinucleotide or as the two mononucleotides. It is not clear whether the action of the non-specific phosphatase on an artificially-prepared, equimolecular mixture of the four mononucleotides has been studied (although the individual mononucleotides have been so examined by Bredereck, Beuchelt and Richter ), but Kobayashi has found that guanylic acid is hydrolyzed more readily than adenylic acid which, in turn, is hydrolyzed more readily than the pyrimidine nucleotides. Furthermore, Bredereck, et oZ. have shown that mild chemical hydrolysis of ribosenucleic acid with aqueous pyridine at 100° gives guanylic acid (G) plus a trinucleotide composed of adenylic (A), cytidylic (C), and uridylic (U) acids. On further hydrolysis in aqueous pyridine, adenylic acid is split off. Hence, in ribosenucleic acid, (G) is at one end of the molecule and, in the trinucleotide, (A) is at one end of the molecule. Possible formulas for the tetranucleotide are therefore... 

Finally, perhaps an explanation for the beneficial effects of coenzyme A (CoA), malate and pyruvate for the extracellular in vitro growth of P. lophurae found by Trager (1952) and interpreted by Moulder (1962) to neatly explain the shift in pattern of carbohydrate metabolism accompanying liberation of parasites from the host cell. .. (The) lack of CoA in free parasites logically explains the lessened rate of pyruvic acid oxidation via the Krebs cycle. It is difficult to escape the conclusion that the inability of plasmodia to synthesize CoA extracellularly results in extensive dislocations in glucose metabolism, which in turn contribute heavily to the restriction of the malarial parasite to an intracellular habitat is this malate and pyruvate could be linked to the generation of dihydronicotinamide adenine dinucleotide (NADH) for glycolysis, and a CoA deficiency could limit activity in pathways other than the TCA cycle. 

Oxidative reactions in catabolic sequences involve the removal of electrons from an intermediate. This process is controlled by dehydrogenases and often involves the participation of the cofactor nicotinamide adenine dinucleotide (NAD or NAD+). Electrons from the donor are transferred to NAD in the form of the hydride ion [ H-] to produce reduced NAD (NADH). In many reactions two hydrogen atoms are removed from the substrate, one in the form of the hydride ion, the other liberated as a proton accordingly, the reduction of NAD+ is often written as... 

Riboflavin readily decomposes through the action of light and of alkalies. It is sparingly soluble in water but can be extracted by adding pyridine or acetic acid or by using dilute mineral acids. It is stable in acid solution. Vitamin Bg occurs in nature as phosphate ester and, further, as adenine dinucleotide or linked to protein it must be liberated by enzymatic treatment before determination. 

A peculiar specificity of action was found with an enzyme from guinea pig liver nuclei. This enzyme splits ordinary dinucleotide bonds to form 3 -phosphate esters. When it is given cyclic nucleotides as substrates, on the other hand, it liberates exclusively 2 esters. It is not certain, however,... 

The free nicotinamide liberated in Eq. (10a) would be converted to DPN, hence giving a net synthesis of an additional mole of DPN. It is possible that pyridine-3-aldehyde and pyridyl-3-carbinol are poor precursors of DPN in comparison to the 3-CH3-pyridine, because they may be rapidly converted to nicotinic acid at the free base stage whereas the picoline derivative is not. Tryptophan conversion to nicotinamide may also occur with intermediates at the riboside, ribonucleotide, or dinucleotide stage. That such intermediates may exist is suggested by the studies of Yanofsky i09) who has obtained evidence for the synthesis of anthranilic acid ribonucleotide in E. colt. 

Liberation of the Solid-Phase-Supported and Protected Dinucleotide... 

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