The formation of a  -(1 leads to 4)-D-galactan chain catalysed by a Phaseolus aureus enzyme.
With a particulate enzyme preparation from Phaseolus aureus hypocotyls, UDP-alpha-d-[U-(14)C]galactose served as a precursor for a number of products. One of these products was characterized as a beta-(1-->4)-linked galactan. The ADP-, GDP-, TDP- and CDP- derivatives of alpha-d-galactose did not serve as biosynthetic precursors for any products insoluble in 70% ethanol, nor as substrates for a sugar nucleotide 4-epimerase which is present in the particulate enzyme preparation. The (14)C-labelled beta-(1-->4)-galactan is alkali-insoluble and was characterized by analysis of partial acetolysis products. The labelling pattern of the [(14)C]oligosaccharides derived from acetolysis indicates that (1) only slightly more than two [(14)C]galactose moieties are added to the growing polysaccharide chain on average, and (2) these additions take place at the reducing end of the polysaccharide chain. The radioactive beta-(1-->4)-linked galactan chain represented 8.5% of the radioactivity initially added, and 20% of the water- and butanol-insoluble products derived from UDP-alpha-d-[(14)C]galactose. Total hydrolysis of the alkali-insoluble fraction of Phaseolus aureus hypocotyl yielded d-glucose and d-mannose in a 5:1 ratio but no detectable quantities of d-galactose. A trace quantity of a radioactive disaccharide, identified as (1-->3)-linked galactobiose, was isolated from the partial acetolysate of the alkali-insoluble [(14)C]polysaccharide material. Also isolated from this partial acetolysate was a C-1 derivative of [(14)C]galactose, which could not be identified. An alkali-soluble galactose-containing polysaccharide was also synthesized in this enzymic reaction, and represented 20% of the water- and butanol-insoluble products derived from UDP-alpha-d-[(14)C]galactose. The spectrum of radioactive oligosaccharides produced by partial acetolysis of this alkali-soluble polysaccharide material was different from that obtained from the alkali-insoluble polysaccharide, indicating a different structure.
D002238:Carbohydrate Epimerases; D002247:Carbon Isotopes; D002854:Chromatography, Paper; D004590:Electrophoresis, Paper; D005690:Galactose / Q000378:metabolism*; D006602:Hexosyltransferases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009702:Nucleoside Diphosphate Sugars; D009844:Oligosaccharides / Q000032:analysis; D010084:Oxidation-Reduction; D010504:Periodic Acid; D010944:Plants / Q000201:enzymology*; D011134:Polysaccharides / Q000032:analysis / Q000096:biosynthesis*; D012995:Solubility; D014539:Uridine Diphosphate Sugars / Q000378:metabolism
D002247:Carbon Isotopes; D009702:Nucleoside Diphosphate Sugars; D009844:Oligosaccharides; D011134:Polysaccharides; D014539:Uridine Diphosphate Sugars; D010504:Periodic Acid; D006602:Hexosyltransferases; D002238:Carbohydrate Epimerases; D005690:Galactose