Fructose oxidation

The fatty acid because it is more highly reduced than the sugar (more hydrogens per mole to burn). The AG of hexanoic acid oxidation will be more negative than the AG of fructose oxidation. 

Attempts to provide further evidence on the role of insulin on the hexokinase reaction include studies on insulin s effect on certain pathways of carbohydrate metabolism that bypass the hexokinase reaction. For example (1) absence of an effect of insulin on the usage of a sugar such as fructose, which is metabolized after phosphorylation by enzymes other than hexokinase (2) the fact that fructose oxidation is unaltered in alloxan-diabetic animals and (3) the effect of insulin on glycogen biosynthesis in diaphragm or liver slices from [ " Qglucose and labeled pyruvate. 

The existence of an enzyme reaction for fructose-1,6-diphosphate which does not appear to lead to the usual products of glycolysis calls attention to older data on the oxidation of fructose by brain cortex and retina without the production of the lactic acid normally formed by these tissues from glucose. It had been hypothesized that an alternate route of fructose oxidation existed in those tissues. 

Similarly, in 2005, Eerapontova and Gorton demonstrated DET of o-fructose dehydrogenase from Gluconobacter industrius by immobUizalion on gold electrodes modified with an alkanethiol self-assembled monolayer (SAM). A formal redox potential of -0.158 and -0.089 V was observed at pH 5.0 and 4.0, respectively. It was found that a positively charged SAM was essential for DET and the potential for fructose oxidation could be shifted from -0.080 to -0.120 V by simply varying the functional groups of the SAM [118]. 

When exposed to sunlight, it is converted to a white insoluble resin, disacryl. Oxidized by air to propenoic acid small amounts of hy-droquinone will inhibit this. Bromine forms a dibromide which is converted by barium hydroxide into DL-fructose. The acrid odour of burning fats is due to traces of propenal. It is used in the production of methionine and in controlled polymerization reactions to give acrolein polymers. ... 

Draw a structural formula for the fructose molecule (remember that fructose is an isomer of glucose). Explain why fructose cannot be oxidized to a six-carbon acid. 

S (2)-hydroxy-3-butenenitrile from acrolein and HCN trans hydrocyanation using, for instance, acetone cyanohydrin Hydrolysis of nitriles to amides, e.g. acrylonitrile to acrylamide Isomerization of glucose to fructose Esterifications and transesterifications Interesterify positions 1 and 3 of natural glycerides Oxidation of glucose to gluconic acid, glycolic acid to glyoxalic acid... 

Figure 17.12 Direct electrocatal3ftic oxidation of D-fnictose at a glassy carbon electrode painted with a paste of Ketjen black particles modified with D-fructose dehydrogenase from a Gluconobacter species. The enzyme incorporates an additional heme center allowing direct electron transfer from the electrode to the flavin active site. Cyclic voltammograms were recorded at a scan rate of 20 mV s and at 25 + 2 °C and pH 5.0. Reproduced by permission of the PCCP Owner Societies, from Kamitaka et al., 2007.

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