Hydrogen isotope effects in the cyclization of D-glucose 6-phosphate by myo-inositol-1-phosphate synthase.
myo-Inositol-1-phosphate synthase (EC 5.5.1.4) from rat testis, Acer pseudoplatanus L. cell culture and Oryza sativa L. cell culture, converted D-[5-3H]glucose 6-phosphate to myo-[2-3H]inositol 1-phosphate at rates ranging from 0.21 to 0.48 that of unlabeled substrate. D-[3-3H]- and D-[4-3H]glucose 6-phosphate were converted at approximately the same rate as that of unlabeled substrate. In the case of testis enzyme, storage as a frozen solution further lowered the rate with D-[5-3H]glucose 6-phosphate as substrate. When the reaction was run in [3H]water, no 3H appeared in myo-inositol 1-phosphate but a small amount was recovered in substrate isolated from the final reaction mixture. These data support the involvement of carbon 5 of D-glucose 6-phosphate in the mechanism proposed for this conversion.
D000818:Animals; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D002478:Cells, Cultured; D005958:Glucosephosphates / Q000378:metabolism*; D008297:Male; D007296:Myo-Inositol-1-Phosphate Synthase / Q000378:metabolism*; D010944:Plants; D051381:Rats; D013737:Testis / Q000201:enzymology; D014316:Tritium
D005958:Glucosephosphates; D014316:Tritium; D002238:Carbohydrate Epimerases; D007296:Myo-Inositol-1-Phosphate Synthase