Quantiation of epoxide hydrolase released from hyperplastic nodule and hepatoma microsomes

Incubation conditions have been established for the release of epoxide hydrolase from rat liver hyperplastic nodule and hepatoma microsomes. This protein was quantitated by electroimmunoassay and by enzymatic activity. Significant amounts of epoxide hydrolase were released from nodule and hepatoma microsomes but not from normal microsomes. Analytical gel electrophoresis showed that nodule and hepatoma microsomes, but not normal microsomes, also released a polypeptide coincident with purified epoxide hydrolase plus another polypeptide with an apparent subunit molecular weight of 43,000. Hyperplastic nodule and hepatoma cytosol fractions had significant amounts of epoxide hydrolase, but normal liver cytosol fraction had no immunologically detectable hydrolase. The release of these proteins appears to be a characteristic of the state of pre- or actual neoplastic endoplasmic reticulum.