Catalysis of Orotidine 5 -Monophosphate

As a model for interactions present in the active site of orotidine-5 -monophosphate decarboxylase (ODCase), we investigated the effects of substrate destabilization by a nearby negative charge and stabilization of the carbanion intermediate, due to hydrogen bonds to the carbonyl groups (O-2 and O-4) of orotic acid and its decarboxylation product, using ab initio calculations. Results from these models were comparable with available data, suggesting that the magnitude of the decarboxylation rate enhancement depends on a combination of the charge distance and hydrogen bonding effects. We found that the dipole moment of the proton donor may also play a significant role, implying that the key to the rest of the catalysis lie within the specific interactions of the substrate and the surrounding residues.

Autorentext

Diana L. Shem recibió su B.S en Bioquímica y M.S. en Química de la Universidad Estatal de San Francisco. También recibió una maestría en Educación para la Enseñanza de la Química de la Universidad de Stanford en Palo Alto, California. Sus otros libros incluyen la guía instructiva, "Tutorial de Mathematica para Química Física", disponible gratis en línea.

Klappentext

As a model for interactions present in the active site of orotidine-5 -monophosphate decarboxylase (ODCase), we investigated the effects of substrate destabilization by a nearby negative charge and stabilization of the carbanion intermediate, due to hydrogen bonds to the carbonyl groups (O-2 and O-4) of orotic acid and its decarboxylation product, using ab initio calculations. Results from these models were comparable with available data, suggesting that the magnitude of the decarboxylation rate enhancement depends on a combination of the charge distance and hydrogen bonding effects. We found that the dipole moment of the proton donor may also play a significant role, implying that the key to the rest of the catalysis lie within the specific interactions of the substrate and the surrounding residues.