Crystallographic studies of Arylesterase and Thioesterase
Institute of Molecular Biology, Academia Sinica
The Escherichia coli thioesterase I (E.C. 220.127.116.11) and arylesterase (E.C. 18.104.22.168.) belong to a discrete group of widely distributed esterases (ester hydrolases) (E.C. 3.1), which hydrolyzes the esterase bonds. Thioesterase specially catalyzes the hydrolytic cleavage of fatty acyl-coenzyme A (CoA) thioesters and arylesterase has an aromatic substrate preference. These two enzymes have been demonstrated to be multifunctional enzymes as lipase and esterase. They are therefore expected to have industrial potential such as stereospecific synthesis and hydrolysis of esters. According to the sequence alignment and biochemical assay, they have been shown to contain a novel Gly-Asp-Ser-Leu-Ser motif, which is located close to the N-terminal region and different from the Gly-Xaa-Ser-Xaa-Gly motif found in the middle regions of other typical lipases and esterases, suggesting a unique three-dimensional folding of thioesterase. With this Gly-Asp-Ser-Leu-Ser motif they and seven other proteins from different species form a new subfamily of lipolytic enzymes (Upton & Buckley, 1995). At present, no X-ray crystal structure is available for any member of this family of proteins. Therefore, crystallographic studies of this subfamily of lipolytic enzymes have become an interesting structural-biology work.