Potassium Fructose-1-phosphate

Another feature common to all hexoses is their fragmentation to trioses and related products (such as lactic acid, l-hydroxy-2-propanone, and pyruvaldehyde). l-Hydroxy-2-propanone is formed by heating a solution of D-fructose in potassium acid phosphate buffer solution of pH 6.7 it was proposed that an intermediary 3,4-enediol (s) rearranges to a /3-diketone, which yields (t) by fragmentation of the molecule. Studies by Wolfrom and Schumacher and by Blair and Sowden showed that this mechanism, followed by recombination and aldolization, accounts for some of the observed products. The identification of L-a 2/io-hexulose and DL-a yZo-hexulose was conclusive in this respect, but deuterium studies by Sowden and Thompson proved the minor role of this recombination mechanism in the transformations. 

Harrison, Tarr and Hibbert96 investigated the production of levan from sucrose by the action of Bacillus subtilis Cohn and B. mesentericus Trevisan. Nutrient solutions containing 10% carbohydrate, 0.1% peptone, 0.2% disodium hydrogen phosphate and 0.5% potassium chloride were incubated at 37° for six days. Levan formation occurred only with sucrose and raffinose, and not with melezitose, lactose, maltose, D-xylose, D-glucose or D-fructose. It was therefore suggested that only those carbohydrates with a terminal D-fructofuranose residue were satisfactory substrates for levan formation. 

It had been known from at least the time of Pasteur that the presence of sodium or potassium phosphate aided the progress of a yeast fermentation. Later intensive study showed that a complex group of enzymes (phosphatases and phosphorylases) was responsible for the phosphorylation, dephosphorylation and interconversion of D-glucose 6-phosphate, D-fructose 6-phosphate, D-fructose 1,6-diphosphate and similar substances in various types of cells and muscle tissue. Detailed reviews of the field are available. - A further advance was made in 1936, when Cori and Cori noted that in certain circumstances well-washed frog muscle immersed in a sodium phosphate buffer utilized the inorganic phosphate to produce a new hexose phosphate (the Cori ester). This compound was later shown to be a-D-glucopyranose-l-phosphate and yielded crystalline dipotassium and brucine salts. The Cori ester arose because... 

Trehalose, sucrose, maltose, fructose, raffinose, lactose, glucose Poloxamer 407, Poloxamer 188, polysorbate 80, polysorbate 20, octoxynol-9, polyoxyethylene-(23) lauryl alcohol, polyxyethylene-(20) oleyl alcohol, sodium lauryl sulphate Sodium sulphate, ammonium sulphate, magnesium sulphate, sodium acetate, sodium lactate, sodium succinate, sodium proprionate, potassium phosphate Cyclodextrins, mannitol, sorbitol, glycerol, xylitol, inositol Ascorbic acid, glutathione... 

Whereas sodium participates in metabolism mainly by its cationic properties, potassium is more directly involved in metabolism. Potassium stimulates the activity of a specific enzyme— pyruvic kinase—and is required for the phosphorylation of fructose-1-phosphate to fructose-1,6-diphosphate. Similarly, potassium stimulates acetyl kinase activity. Many alterations in the bioenergetic pathways of the cell are accompanied by changes in the intracellular concentration of potassium. After insulin administration, some of the potassium of the extracellular fluid is transferred inside the cells. During oxidative phosphorylation, potassium accumulates inside the mitochondria, and dinitrophenol uncouples the ion penetration and the oxidation. 

Rat liver extracts also contain two highly specific kinases, namely, glucokinase and fructokinase. Glucokinase, in the presence of ATP and Mg++, forms glucose-6-phosphate fructokinase catalyzes the formation of fructose-l-phosphate. Beef Uver fructokinase, like rat fiver fructokinase, is strongly activated by potassium chloride. Sodium and ammonium ions are relatively inert. The affinity of the enzyme for fructose is very high, the Km being lower than 5 X 10 moles per liter. This is in contrast to muscle fructokinase, which has a very weak aflfinity for its subtrate. 

The fructokinase of rat liver does not react with glucose, mannose, and galactose, but does react with the ketohexoses, fructose, L-sorbose, and D-tagatose. Evidence has been obtained to show that the product of sorbose phosphorylation is probably sorbose-l-phosphate. The enzyme in liver homogenates is considerably more reactive aerobically than anaerobically—a curious and as yet unexplained phenomenon. liver fructokinase requires Mg++ or Mn++ ions for its activity, and evidence has been obtained that Mg++ in combination with ATP is a cosubstrate for the enzyme. Potassium ion in very high concentration increases the rate of the transphosphorylation. 

The oxidation of aldoses and sugar phosphates by Cr(VI) has been reviewed (23 refs.). The kinetic behaviour and the relative reactivities of several trioses, tetioses, pentoses and hexoses, amino sugars, and methylated sugars towards potassium permanganate in perchloric acid solution have been examined. Mechanisms have been proposed for the oxidation of arabinose and xylose by iodine in alkaline solution and by alkaline NBS under Ru(Vni)-catalysis. For the oxidation of monosaccharides by sodium iV-bromobenzenesulfonamide in alkaline media, reaction via 1,2-enediol intermediates has been postulated. 1 1 Stoichiometry has been observed in the oxidation of D-fructose with PCC. ... 

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