Active at neutral pH. Several variants of this enzyme exist; the human erythrocyte enzyme is relatively specific for removal of N-acetylalanine from peptides. Displays dipeptidyl-peptidase activity on glycyl-peptides, perhaps as a result of mis-recognition of the glycyl residue as an uncharged N-acyl group. Inhibited by diisopropyl fluorophosphate. In peptidase family S9 (prolyl oligopeptidase family).