Hormone-sensitive lipase (HSL) plays an important role in the regulation of rodent fat cell lipolysis. It is regarded as an adipose tissue-specific enzyme whose sole metabolic role is the catalysis of hormone-stimulated lipolysis in mammalian cells. In this report we describe the functional and structural analysis of an EstE5 protein from a soil metagenome library. Function analysis results indicated that EstE5 preferentially hydrolyzes short-chain ester compounds, and our kinetic Studies revealed the optimal pH and temperature. Based on the structural analysis, we defined the active site and the binding pocket. Structurally, EstE5 belongs to the HSL family and these structural studies may have applications in the production Of Value-added products, including pharmaceuticals. (C) 2008 Elsevier Inc. All rights reserved.