Fructose phosphate , detection

Phosphomonoesters (PME) Certain intermediaries in the glycolytic pathway such as glucose and fructose phosphates resonate in this region of the spectrum and are sometimes detected. More usually, the PME peak comprises the lipid precursors phos-phocholine and phosphoethanolamine. 

Pyruvate kinase (PK) is one of the three postulated rate-controlling enzymes of glycolysis. The high-energy phosphate of phosphoenolpyruvate is transferred to ADP by this enzyme, which requires for its activity both monovalent and divalent cations. Enolpyruvate formed in this reaction is converted spontaneously to the keto form of pyruvate with the synthesis of one ATP molecule. PK has four isozymes in mammals M, M2, L, and R. The M2 type, which is considered to be the prototype, is the only form detected in early fetal tissues and is expressed in many adult tissues. This form is progressively replaced by the M( type in the skeletal muscle, heart, and brain by the L type in the liver and by the R type in red blood cells during development or differentiation (M26). The M, and M2 isozymes display Michaelis-Menten kinetics with respect to phosphoenolpyruvate. The Mj isozyme is not affected by fructose-1,6-diphosphate (F-1,6-DP) and the M2 is al-losterically activated by this compound. Type L and R exhibit cooperatively in... 

Lohmann118 detected an enzyme in muscle extracts, found later in plants and yeasts,104Co) 117,118 termed phosphoglucoisomerase, (optimum pH 9), which catalyzes the interconversion of D-glucose 6-phosphate (XVI) and D-fructose 6-phosphate (XVII). At equilibrium, which is attained rapidly, there is about 70 % of the former and 30 % of the latter. In a similar conver-... 

Some very nice engineering and experimental work was performed by Pollard et al. in measuring a fungal fermentation in real time.21 The work was performed on a 75-1 fermentor and showed detection limits for fructose, glutamate, and proline in production matrices of 0.1,0.5, and 0.5 g/1, respectively. Glucose and phosphate were measured in a 280-1 pilot scale batch with detection limits for both of 0.1 g/1. 

Genetic deficiency of fructokinase is benign and often detected incidentally when the urine is checked for glucose with a dipstick. Fructose 1-phosphate aldolase deficiency is a severe disease because of accumulation of fructose 1-phosphate in the liver and renal proximal tubules. Table 1-12-4 compares the two conditions. Symptoms are reversed after removing fructose and sucrose from the diet. 

Later, Yoshida et al. reported the dehydration of fructose to HMF in a batch-type reactor under subcritical water (sub-CW) and with different zirconium phosphate solid acid catalysts at 240°C (Scheme 7) [77]. Over amorphous zirconium phosphate, 80% of fructose was converted after 120 s affording HMF with a selectivity of 61%. Interestingly, no side product stemming from the rehydration of HMF was detected in this case. However, soluble polymers and furaldehyde were detected as side products. Remarkably, zirconium phosphate solid catalysts were stable under subcritical water conditions and were reused without any loss of their activity. 

The problems associated with the separation of phosphate esters are the tendency of the spots to diffuse difficulty of reproducing RF values variability of RF values with complexity of the mixture being resolved and distance of solvent travel proper purification and equilibration of the filter paper effect of inorganic ions in natural mixtures and the choice of suitable solvent mixtures for desired separations. The problem of detecting the separated spots is somewhat simpler. In addition to methods applicable to the detection of reducing sugars (e.g., use of aniline salts fructose esters are detected by naphthoresorcinol-acid), methods depending on phosphomolybdate formation are most commonly used. Hanes and Isher-... 

An alternative method for detecting the fructose produced involves the use of ffuctokinase (EC 2.7.1.4), phosphoglucose isomerase, and glucose-6-phosphate dehydrogenase (EC 1.1.1.49), measuring in this case the nicotinamide-adenine dinucleotide phosphate, reduced form (NADPH) produced. ... 

A deficiency of fructose-1-phosphate aldolase produces this rare disorder with hypoglycemia and liver failure. Fructose ingestion inhibits glycogenolysis and giuconeogenesis, producing hypoglycemia. Early detection is important because this condition responds to a diet devoid of sucrose and fructose. 

This fructokinase catalyzes phosphorylation to afford D-fructose 6-phosphate this enzyme activity was detected in the cytoplasm of Streptococcus faecalis,321 Echinococcus granulosus,322 and in pea.323... 

The existence of two separate mechanisms for the synthesis of sucrose raises the question of their respective roles in vivo. Experiments in which C Mabeled n-glucose was supplied to plants have shown that the d-fructofuranosyl moiety of sucrose becomes highly labeled before any label appears in the free D-fructose pool, suggesting that this monosaccharide is not an intermediate in sucrose synthesis. On the other hand, d-fructose 6-phosphate becomes labeled before sucrose, and small proportions of sucrose 6 -phosphate have also been detected among the labeled pro-ducts. These results are compatible with the hypothesis that sucrose 6 -phosphate is synthesized first and is subsequently hydrolyzed to free sucrose. Such a pathway would be clearly irreversible, since it includes a hydrolytic step, and could account for the large accumulation of sucrose in many plants. 

Panek reported similar findings with extracts of bakers yeast, but detected trehalose, not trehalose 6-phosphate however, this may have been due to the presence of a highly active phosphatase. Elander studied the trehalose 6-phosphate synthetase of yeast after purifying the enzyme about 27-fold. The synthesis of trehalose 6-phosphate was inhibited by uridine 5 -pyrophosphate, which was competitive with UDP-D-glucose, and also by uridine 5 -triphosphate (UTP). It was also inhibited by 20 mM concentrations of inorganic phosphate, n-glucosyl phosphate, D-fructose 6-phosphate, o-mannose 6-phosphate, and trehalose 6-phosphate. n-Mannose 6-phosphate and trehalose 6-phosphate were competitive with n-glucose 6-phosphate. Free trehalose had no efiFect on the reaction. 

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