3v3r

Publication Abstract from PubMed

GES-1 is a class A extended-spectrum beta-lactamase conferring resistance to penicillins, first-, second-generation cephalosporins and to ceftazidime. However, GES-1 poorly hydrolyzes aztreonam and cephamycins, and exhibits very low k(cat) values for carbapenems. Twenty-two GES variants have been discovered thus far, differing from each other by 1-3 amino acid substitutions that affect substrate specificity. GES-11 possesses a Gly243Ala substitution which seems to confer this variant an increased activity against aztreonam and ceftazidime. GES-12 differs from GES-11 by a single Thr237Ala substitution while GES-14 differs from GES-11 by the Gly170Ser mutation which is known to confer increased carbapenemase activity. GES-11 and GES-12 were kinetically characterized and compared with GES-1 and GES-14. Purified GES-11 and GES-12 showed strong activities against most tested beta-lactams with the exception of temocillin, cefoxitin and carbapenems. Both variants showed a significantly increased rate of hydrolysis of cefotaxime, ceftazidime and aztreonam. On the other hand, GES-11, GES-12 (and GES-14) variants all containing Ala243 exhibited increased susceptibility to classical inhibitors. The crystallographic structures of the GES-11 and GES-14 beta-lactamases were solved. The overall structures of GES-11 and GES-14 are similar to that of GES-1. The Gly243Ala substitution caused only subtle local rearrangements, notably in the typical carbapenemase disulfide bond. The active sites of GES-14 and GES-11 are very similar, the Gly170Ser substitution leading only to the formation of additional hydrogen bonds of the Ser residue with the hydrolytic water and the Glu166 residue.

Kinetic and crystallographic studies of extended spectrum GES-11, GES-12 and GES-14 beta-lactamases.,Delbruck H, Bogaerts P, Kupper MB, de Castro RR, Bennink S, Glupczynski Y, Galleni M, Hoffmann KM, Bebrone C Antimicrob Agents Chemother. 2012 Aug 20. PMID:22908160^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.