CONICET | Buscador de Institutos y Recursos Humanos

Abstract: Metallo- -lactamases hydrolyze most -lactam antibiotics. The lack of a successful inhibitor forthem is related to the previous failure to characterize a reaction intermediate with a clinically useful substrate.Stopped-ﬂow experiments together with rapid freeze-quench EPR and Raman spectroscopies were usedto characterize the reaction of Co(II)-BcII with imipenem. These studies show that Co(II)-BcII is able tohydrolyze imipenem in both the mono- and dinuclear forms. In contrast to the situation met for penicillin,the species that accumulates during turnover is an enzyme-intermediate adduct in which the -lactambond has already been cleaved. This intermediate is a metal-bound anionic species with a novel resonantstructure that is stabilized by the metal ion at the DCH or Zn2 site. This species has been characterizedbased on its spectroscopic features. This represents a novel, previously unforeseen intermediate that isrelated to the chemical nature of carbapenems, as conﬁrmed by the ﬁnding of a similar intermediate formeropenem. Since carbapenems are the only substrates cleaved by B1, B2, and B3 lactamases,identiﬁcation of this intermediate could be exploited as a ﬁrst step toward the design of transition-state-based inhibitors for all three classes of metallo- -lactamases.