title: Ribulose-1,5-bisphosphate carboxylase: primary deuterium kinetic isotope effect using [3-2H]ribulose 1,5-bisphosphate.
abstract: The primary deuterium kinetic isotope effect for the reaction of [3-2H]ribulose 1,5-bisphosphate with CO2 in the reaction catalyzed by ribulose-1,5-bisphosphate carboxylase has been determined. By use of highly purified substrates containing less than 0.13% of the C-3 epimer xylulose 1,5-bisphosphate (this material is known to be a potent competitive inhibitor), the kinetic isotope effect has been shown to be 1.2 +/- 0.2 (Vmax) and 1.3 +/- 0.3 (Vmax/Km). These values are clearly too small to be intrinsic isotope effects for the rate-limiting removal of the C-3 proton from ribulose 1,5-bisphosphate. The results confirm the conclusions from the tritium experiments reported in the previous two papers and emphasize the fine balance between the forward and reverse reactions of the enediol intermediate.
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002262:Carboxy-Lyases / Q000378:metabolism*; D003903:Deuterium / Q000378:metabolism; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D010428:Pentosephosphates / Q000378:metabolism*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D012274:Ribulosephosphates / Q000378:metabolism*
chemical_list: D010428:Pentosephosphates; D012274:Ribulosephosphates; D009243:NAD; D002245:Carbon Dioxide; C001933:ribulose-1,5 diphosphate; D003903:Deuterium; D002262:Carboxy-Lyases; D012273:Ribulose-Bisphosphate Carboxylase