The C-5 hydrogen isotope-effect in myo-inositol 1-phosphate synthase as evidence for the myo-inositol oxidation-pathway.
The hydrogen isotope-effect that occurs in vitro during myo-inositol1-phosphate synthase-catalyzed conversion of D-[5-3H]glucose 6-phosphate into myo[2-3H]inositol 1-phosphate has been used to compare the functional role of the nucleotide sugar oxidation-pathway with that of the myo-inositol oxidation-pathway in germinating lily pollen. Results reveal a significant difference between the 3H/14C ratios of glucosyl and galactosyluronic residues from pectinase-amyloglucosidase hydrolyzates of the 70% ethanol-insoluble fraction of D-[5-3H, 1-14C]glucose-labeled, germinating lily pollen. This isotope effect at C-5 of D-glucose that occurred during its conversion into D-galactosyluronic residues of pectic substance is not explained by loss of 3H when UDP-D-[5-3H, 1-14C]glucose is oxidized by UDP-D-glucose dehydrogenase from germinating lily pollen. The evidence obtained from this study favors a functional role for the myo-inositol oxidation-pathway during in vivo conversion of glucose into galactosyluronic residues of pectin in germinating lily pollen.
D002238:Carbohydrate Epimerases / Q000378:metabolism*; D002250:Carbon Radioisotopes; D007700:Kinetics; D007296:Myo-Inositol-1-Phosphate Synthase / Q000378:metabolism*; D010944:Plants / Q000201:enzymology*; D011058:Pollen; D011865:Radioisotope Dilution Technique; D014316:Tritium
D002250:Carbon Radioisotopes; D014316:Tritium; D002238:Carbohydrate Epimerases; D007296:Myo-Inositol-1-Phosphate Synthase