DPEP1 (EC 3.4.13.11) is a kidney membrane enzyme that hydrolyzes a variety of dipeptides and is implicated in renal metabolism of glutathione and its conjugates, e.g., leukotriene D4 (Kozak and Tate, 1982). DPEP1 is responsible for hydrolysis of the beta-lactam ring of antibiotics, such as penem and carbapenem (Campbell et al., 1984). Earlier, beta-lactamase enzymes were thought to occur only in bacteria, where their probable function was in protecting the organisms against the action of beta-la