Molecular mass of inhibitor-2 from rabbit liver

Inhibitor-2 was partially purified from rabbit liver by fractionation with ammonium sulphate, heat treatment at 100 degrees C, precipitation with trichloroacetic acid, chromatography on DEAE-cellulose at pH 8.5 and 5.0 and gel filtration on Sephadex G-100 (Stokes radius, 3.4 nm). The protein behaved as a single component at each step and migrated on SDS-polyacrylamide gels as a 31 kDa protein. Its properties were indistinguishable from those of skeletal muscle inhibitor-2. The results disagree with the report of Khandelwal and Zinman (J. Biol. Chem. (1978) 253, 560-565) that hepatic inhibitor-2 is a 14 kDa protein.