activates the decarboxylation of 5-fluoroorotate. This activation is due to the utilization of binding energy from interactions between OMPDC and activator
decarboxylation of substrate analog 5'-deoxy-5-fluoroorotidine is activated. Decarboxylation of truncated substrate analog 1-(beta-D-erythrofuranosyl)-5-fluoroorotic acid is activated by exogenous phosphite dianion, but the 5-F substituent results in only a 0.8 kcal stabilization of the transition state for the phosphite-activated reaction
the 5'-phosphate group of the substrate activates the enzyme 240000000fold. The binding of orotidine 5'-monophosphate is accompanied by a conformational change of the enzyme from an open, inactive conformation to a closed, active conformation. As the substrate traverses the reaction coordinate to form the stabilized vinyl carbanion/carbene intermediate, interactions that destabilize the carboxylate group of the substrate and stabilize the intermediate are enforced. The activation is equivalently described by an intrinsic binding energy of 11.4 kcal/mol. The residues that directly contact the 5'-phosphate group, participate in a hydrophobic cluster near the base of the active site loop that sequesters the bound substrate from the solvent, or that form hydrogen bonding interactions across the interface between the mobile and fixed half-barrel domains of the (beta/alpha)8-barrel structure. The data support a model in which the intrinsic binding energy provided by the 5'-phosphate group is used to allow interactions both near the N-terminus of the active site loop and across the domain interface that stabilize the complexes of the enzyme in the active closed conformation with the substrate or with the substrate intermediate with the destabilized carboxylate group relative to the complex of the enzyme in the open inactive conformation with the substrate
enzyme ScOMPDC-catalyzed decarboxylation of 5-fluoroorotate is stabilized by 5.2, 7.2, and 9.0 kcal/mol, respectively, by 1.0 M phosphite dianion, D-glycerol 3-phosphate and D-erythritol 4-phosphate, so that binding interactions between both the substrate phosphodianion and the ribosyl hydroxyls are utilized to activate ScOMPDC for catalysis
strong phosphite dianion activation of ScOMPDC-catalyzed decarboxylation of of 1-(beta-D-erythrofuranosyl)-5-fluoroorotate (FEO), of 5-fluoroorotate (FO) and of 1-(beta-D-erythrofuranosyl)-orotic acid. Utilization of intrinsic dianion energy
the activation with substrate 1-(beta-D-erythrofuranosyl)-orotate is due to the utilization of binding energy from interactions between OMPDC and activator to drive a complex conformational change from inactive open OMPDC (EO) to the active closed caged complex (EC), where EC is stabilized relative to EO by interactions between dianions and the side chains of Q215, Y217, and R235