Purification and characterization of a soluble epoxide hydrolase from rabbit liver

A method for the extensive purification of rabbit liver cytoplasmic epoxide hydrolase is described. The end-product, which was purified 550-fold with respect to the cytosolic fraction, appeared to be more than 85% pure. Results indicate that the enzyme is a dimer of molecular weight 110 000 and consists of two subunits, which are identical or very similar (Mr 57 000) and possess N-terminal serine. Evidence for the existence of aggregates of higher molecular weight was also obtained. The catalytic properties of the cytoplasmic enzyme with styrene oxide as substrate (Km = 3.4 mM; V = 3480 nmol mg-1 min-1) differed markedly from the values published for the microsomal hydrolase.