Loewus M W, Loewus F A
Carbohydr Res. 1980 Jul;82(2):333-42. doi: 10.1016/s0008-6215(00)85707-9.
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.
肌醇1-磷酸合酶催化D-[5-³H]葡萄糖6-磷酸转化为肌醇[2-³H]1-磷酸的体外过程中出现的氢同位素效应，已被用于比较核苷酸糖氧化途径与肌醇氧化途径在百合花粉萌发过程中的功能作用。结果显示，在D-[5-³H, 1-¹⁴C]葡萄糖标记的萌发百合花粉70%乙醇不溶部分的果胶酶-淀粉葡糖苷酶水解产物中，葡萄糖基和半乳糖醛酸残基的³H/¹⁴C比值存在显著差异。D-葡萄糖在转化为果胶物质的D-半乳糖醛酸残基过程中，在C-5处出现的这种同位素效应，不能用萌发百合花粉的UDP-D-葡萄糖脱氢酶氧化UDP-D-[5-³H, 1-¹⁴C]葡萄糖时³H的损失来解释。这项研究获得的证据支持肌醇氧化途径在萌发百合花粉体内将葡萄糖转化为果胶的半乳糖醛酸残基过程中的功能作用。
