PURIFICATION OF PROTEIN CARBOXYMETHYLASE FROM OX BRAIN

— The enzyme protein carboxymethylase from the soluble fraction of ox brain was purified to electrophoretic homogeneity. Brain protein carboxymethylase activity was also detected in a membrane‐bound form which could only be solubilized by treatment with detergent. The solubilized membrane‐bound form differed from the ‘native’ soluble form in that the former irreversibly lost activity on removal of the detergent. The two forms, however, have several similarities, having a molecular weight of 35,000, a K m of 2.7 × 10 −6 M for S ‐adenosyl‐L‐methionine, and a pH optimum of 6.2 when ovalbumin was used as the methyl acceptor.