Multiplicity of carboxylesterase isozymes in mammals and humans: role in metabolic activation of prodrugs

The mammalian carboxyle sterase comprise a multigene family, the gene products of witch are localized in the endoplasmic reticulumo f many tissues. These enzymes efficiently catalyze the hydrolysis of a variety of drugs or prodrugs containing ester- and amide-bond to the respective free acids and alcohol. Since ester derivatives of therapeutic agents have been in use as prodrugs, carboxylesterase are a major determinant of the pharmacokinetic behavior of most prodrugs, and the activity can be influenced either by direct interactions of a variety of compounds either directly or at the level of enzyme regulation. On the other hand, mammalian carboxylesterases represent a multigene family the products of which are localized in the endoplasmic reticulum of many tissues. Among various tissues of animals, the highest hydrolase activity towards various substrates is found in the liver. These hydrolase activities are present in a number of tissues in addition to the liver. Humans also express carboxylesterase in liver, small intestine, brain, kidney, lung, and plasma. Since a significant number of drugs are metabolized by carboxylesterase, altering the activity of this enzyme expressed in each tissue has important clinical implications.. However little is known about the differences in structure and hydrolytic capability of carboxylesterase isozymes expressed in each tissues of humans. In the present study, we have undertaken the structural characterization of carboxylesterase isozymes expressed in human liver, small intestine and brain to learn more about the molecular basis responsible for their functional differences.