Catalyzes the deacylation of 7 beta-(4-carboxybutanamido)cephalosporanic acid (glutaryl-7-aminocephalosporanic acid or GL-7-ACA) to 7-aminocephalosporanic acid (7-ACA). Cannot efficiently use cephalosporin C (CPC), penicillin G, or ampicillin as substrates. (7R)-7-(4-carboxybutanamido)cephalosporanate + H2O = (7R)-7-aminocephalosporanate + glutarate Heterodimer of a small subunit and a large subunit processed from the same precursor. Belongs to the peptidase S45 family.