We have isolated a near full-length cDNA encoding human leukotriene A4 (LTA4) hydrolase from a human spleen cDNA library. The mature form of the enzyme consists of 610 amino acid residues and its molecular weight is calculated to be 69,153. The cDNA was inserted into an expression vector (pUC 9) and expressed in Escherichia coli. The fusion protein (EX85) possessed the LTA4 hydrolase activity with kinetic properties similar to the native enzyme.