COMPARISON OF SOLUBLE AND MEMBRANE-BOUND PYROGLUTAMYL PEPTIDASE-I ACTIVITIES IN RAT-BRAIN TISSUES IN THE PRESENCE OF DETERGENTS

Pyroglutamyl peptidase I activity from soluble and membrane-bound frac tions of rat brain homogenates is inhibited by the presence of sodium deoxycholate but not by triton X-100. Biobeads SM2, a polystyrene adso rbent reported to be useful in removing detergents from aqueous soluti ons, inhibits enzymatic activity in both fractions regardless of the p resence of these detergents, probably because of partial adsorption of the enzyme by the polymeric microspheres. These effects seem to be en zyme-specific since other aminopeptidase activities are not affected b y detergents or biobeads. The results suggest that soluble and membran e-bound forms of the enzyme represent the same protein in two differen t cell compartments.