Cloning and expression of a gene from Isochrysis galbana modifying fatty acid profiles in Escherichia coli

An ester hydrolase gene from the microalga Isochrysis galbana was cloned and expressed in Escherichia coli BL21 Rosetta 2?. The full-length putative gene has 1,146 base pairs and codes for a 381-amino acid polypeptide. The predicted molecular mass of the deduced protein is approximately 42.31 kDa, with a theoretical pI of 9.37. Slight similarity and identity were observed between the microalga sequence and various α/β-fold hydrolases found in diverse phyla. The catalytic triad corresponds to residues Ser²⁵⁴, Asp³⁰⁹, and His³⁴¹, with the nucleophilic catalytic residue Ser²⁵⁴ located in the pentapeptide consensus motif G-X-S²⁵⁴-X-G. The activity of the enzyme was established by fatty acid profile analysis of the membrane lipids. The expression of the protein in E. coli shifted the fatty acid composition predominantly towards C16:1 and C18:1 fatty acids. This enzyme is called I. galbana thioesterase/carboxylesterase (or IgTeCe). This novel gene is shown to have a potential for use in metabolic engineering to enhance the lipid yields of microalgae.