PROPERTIES OF RAT-BRAIN DIPEPTIDYL AMINOPEPTIDASES IN THE PRESENCE OFDETERGENTS

Rat brain dipeptidyl aminopeptidases I to IV were assayed in the solub le and membrane-bound fractions of rat brain, and the effects of the d etergents Triton X-100 and sodium deoxycholate on their activities wer e studied. Dipeptidyl aminopeptidases I and II were significantly inhi bited in the presence of sodium deoxycholate, but were not affected by the presence of Triton X-100. However, dipeptidyl aminopeptidase III was nor influenced by either detergent, whereas the activity of dipept idyl aminopeptidase IV was stimulated in the presence of Triton X-100, but remained unaffected by deoxycholate. These effects were partially or totally reversed after detergents were removed from the medium wit h adsorbent polymeric beads. Although detergents may have different, e ffects on each DAP activity, the behavior of each enzyme activity in t he presence of these substances was similar regardless of their subcel lular location. These findings suggest that, as with other aminopeptid ases, each of these proteins corresponds to the same molecular species in two different cell compartments.