title: 1L-myo-inositol 1-phosphate synthase from pollen of Lilium longiflorum. An ordered sequential mechanism.
abstract: 1L-Inositol 1-phosphate synthase (EC 5.5.1.4) devoid of bound NAD+ was isolated from mature pollen of Lilium longiflorum ( Easter lily ). The enzyme has a molecular weight of 157,000 +/- 15,000 and a subunit weight of 61,000 +/- 5,000. Kinetic studies of the uninhibited reaction and of inhibition by 2-deoxy-D-glucose 6-phosphate and NADH show the reaction to be ordered sequential with NAD+ adding first. The Michaelis constants for NAD+ and D-glucose 6-phosphate are 2.4 and 65 microM, respectively. The Ki for 2-deoxy-D-glucose 6-phosphate was 8.7 and 2.0 microM, respectively, when D-glucose 6-phosphate or NAD+ was varied. The Ki for NADH and variable NAD+ was 4.7 microM and, for NADH and variable D-glucose 6-phosphate, 3.9 microM.
mesh_terms: D002238:Carbohydrate Epimerases / Q000302:isolation & purification*; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives; D005958:Glucosephosphates / Q000378:metabolism; D007700:Kinetics; D008433:Mathematics; D008970:Molecular Weight; D007296:Myo-Inositol-1-Phosphate Synthase / Q000302:isolation & purification* / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D011058:Pollen / Q000201:enzymology*
chemical_list: D005958:Glucosephosphates; D009243:NAD; C015785:2-deoxyglucose-6-phosphate; D019298:Glucose-6-Phosphate; D002238:Carbohydrate Epimerases; D007296:Myo-Inositol-1-Phosphate Synthase