title: Transglycosylic reactions of deoxysugars. Biosynthesis of deoxy analogues of starch.
abstract: The biosynthesis of starch was investigated in the reaction catalyzed by plant alpha(1 leads to 4)-glucan phosphorylase using alpha-D-glucopyranosyl phosphate and its deoxy analogues as substrates. It was found that the hydroxyl groups at the positions C-2, C-3, C-4 and C-6 in the glucose moiety of the molecule of alpha-D-glucopyranosyl phosphate are not essential for its substrate properties in the transglycosylic reaction. The affinity of plant (alpha(1 leads to 4)-glucan phosphorylase and the rate of hexose incorporation into alpha(1 leads to 4)-glucan decreases in the following sequence: alpha-D-glucopyranosyl phos-phosphate, 2-deoxy-, 6-deoxy, 4-deoxy, and 3-deoxy-alpha-D-glucopyranosyl phosphate. The deoxyglucosyl analogues of alpha-D-glucosylpyranosyl phosphate act as competitive inhibitors on the elongation reaction of the alpha(1 leads to 4) chains of starch. It was found that more than one residue of 2-deoxy-D-glucose or 6-deoxy-D-glucose can be incorporated into the nonreducing terminus of alpha(1 leads to 4)-glucan chains of starch.
mesh_terms: D003837:Deoxy Sugars; D003847:Deoxyglucose; D007700:Kinetics; D010944:Plants / Q000201:enzymology; D013213:Starch / Q000031:analogs & derivatives* / Q000096:biosynthesis; D000516:alpha-Amylases / Q000378:metabolism
chemical_list: D003837:Deoxy Sugars; D013213:Starch; D003847:Deoxyglucose; D000516:alpha-Amylases