Serine hydrolase that catalyzes the hydrolytic activation of amino acid ester prodrugs of nucleoside analogs such as valacyclovir and valganciclovir. Activates valacyclovir to acyclovir. May play a role in detoxification processes. It is a specific alpha-amino acid ester hydrolase that prefers small, hydrophobic, and aromatic side chains and does not have a stringent requirement for the leaving group other than preferring a primary alcohol. Monomer. May also form homodimers. Expressed at high levels in liver and kidney and lower levels in heart, intestine and skeletal muscle. Belongs to the AB hydrolase superfamily. Lipase family.