A Short Note On Classification Of Β -lactamases

1197 Words Aug 23rd, 2014 5 Pages
1.6.1 Classification of β-lactamases
Two major schemes for classification of β-lactamases are currently in use. The molecular classification of β-lactamases is based on the amino acid sequence homology dividing them into four classes A through D. The enzymes belonging to class A, C and D utilize serine residue for substrate hydrolysis while class B enzymes (metallo-β-lactamases) utilize divalent zinc ions for β-lactam hydrolysis [Ambler R. P. et al, 1991]. The functional classification is based on the substrate and inhibitor profiles of the enzymes [Bush K. et al, 1995; Bush & Jacoby, 2010]. The inhibitors used in this scheme are Clavulanic acid, tazobactam and EDTA. The β-lactamases can be loosely identified based on their substrate specificities as penicillinases, AmpC-type cephalosporinases, extended-spectrum β-lactamases (ESBLs) and carbapenemases. The ESBLs and cephalosporinases constitute the largest group of enzymes capable of hydrolyzing virtually all penicillins and extended-spectrum cephalosporins [Bush, K., 2010].
These enzymes have plagued the effectiveness of penicillins and cephalosporins against Gram negative bacterial infections resulting in more frequent use of carbapenems. The increased use of carbapenems ensued ESBL proliferation and eventual emergence of carbapenemase in bacteria.

Figure 1.5 : Ambler Classification of β-lactamases

Table 1.3 β-lactamases classification schemes modified form (Bush and Jacoby, 2010)
Amber Class Bush-Jacby group…

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