Radiation inactivation analysis of kidney microvillar peptidases

Five membrane peptidases were studied by radiation inactivation analysis of pig kidney microvillar membranes. One heterodimeric enzyme, gamma-glutamyl transferase, presented a target size corresponding to the dimeric Mr. The other enzymes are known to be homodimers. Three of these, aminopeptidase A. aminopeptidase N and dipeptidyl peptidase IV, gave results clearly indicating the monomer to be the target and, hence, in this group the association of the subunits was not essential for activity. The target size for endopeptidase-24.11 was intermediate between those for monomer and dimer and its functional state was not resolved by the experiments.