Biochemistry: The Chemical Reactions of Living Cells, Volume 2 - D. Metzler 1980

Biosynthesis: How New Molecules Are Formed
Selected pathways of carbohydrate and lipid metabolism
Interconversions of nucleotide sugars

Returning to Fig. 12-1, The oxidation of UDP-glucose to UDP-glucuronic acid proceeds in two stages [3a] involving NAD+. UDP-glucuronic acid is subsequently epimerized to UDP-galacturonic acid. Similarly, as shown in the lower part of the scheme, guanosine diphosphate mannose is oxidized to GDP-mannuronic acid, which undergoes epimerization at the 4-position to be converted into GDP-guluronic acid. As shown in the upper part of the scheme, UDP-D-glucuronic acid can epimerize at the 5-position to yield UDP-L-iduronic acid. However, in dermatan sulfate, iduronic acid residues are formed via inversion at the C-5 atom of D-glucuronic acid residues incorporated within the polymer chain [4]. The mechanisms of both these reactions and the decarboxylation of UDP-glucuronic acid to UDP-xylose (top of Fig. 12-1) remain insufficiently studied. Nevertheless, the reader should be equipped to deduce potential Mechanisms for the described reactions.



Last update: 06/08/2026

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