Sugar degradation pathways

Novel sugar degradation pathway in Pyrococcus furiosus... 

Studies on isolated DNA and sugar model compounds have allowed the determination of the main OH-mediated degradation pathways to the 2-deoxyribose moiety. In addition, data are also available on the influence ofthe double-helix structure on the fate of purine and pyrimidine base radicals. 

Numerous publications have been dedicated to the genesis of alkylthiazoles. A model reaction based on a mixture of cysteine/xylose/tributyrin was studied by Ledl and Severin (1973), who proposed the decarboxylation of cysteine into cysteamine (2-aminoethanethiol), followed by a condensation with sugar degradation products and a subsequent oxidation. Mulders (1973c) also proposed a model based on a system of cysteine/cystine/carbohydrates, with the formation of thiazolidines subsequently oxidized into thiazoles. The same pathway has been proposed by Flament (Firmenich, 1973), thiazolidines easily being formed by the reaction of cysteamine with aldehydes. Kato et al. (1973a) also found thiazoles in the volatile compounds produced by the reaction of L-cystine with carbonyl compounds. Similarly,... 

First, a simplified model of DNA, polydeoxyadenylic acid, was shown to be readily cleaved at neutral pH by Mn-TMPyP/KHSOs with spontaneous release of free adenine and, after heating, formation of a rather unstable sugar degradation product identified as 5-methylene-2(5H)-furanone, supporting a C-1 oxidation pathway. The first /3-elimination created a 5 -phosphate end and the second one was accompanied by 5-MF release. The two DNA strands were terminated by phosphate groups (Fig. 6, route A) (282). 

Shu, C-K. Pyrazine formation from amino acids and reducing sugars, a pathway other than Strecker degradation J. Agr. Food Chem. 46 (1998) 1515-1517. Smeeton, B. W. Genetic control of tobacco quahty Recent Adv. Tob. Sci. 13 (1987) 3-26. 

The two-step process of depurination (see the Depurination and depyrimidation Subsection in Section 4.3.1.2) and P-elimination is an important DNA degradation pathway in aqueous medium [45]. Upon depurination, the apurinic site contains a chemically altered sugar that alternates between a cyclic furanose form and an... 

Amino groups of phospholipids, particularly of phosphatidylethanolamine or serine, react with reducing sugars, osones, and other products of sugar degradation to form brown melanoidins. The pathway via Amadori compounds is similar to the case of amino acids (Utzmann and Lederer, 2001). They thus contribute to the darkening of phospholipid concentrates on storage. Melanoidins are partially bleached by lipid hydroperoxides. 

In the intermediate stage, three degradation pathways exist sugar dehydration, sugar fragmentation, and Strecker degradation ... 

Figure 1 Possible pathways for DMHF formation following sugar degradation.

So it can be concluded that in the case of 1-DG, the glycosidic linked sugar in mahose or lactose causes a degradation pathway which is significantly different from glucose and which gives rise to typical disaccharide products. 

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