Words similar to penicillins
Example sentences for: penicillins
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Generally, the S224A and S224K mutants exhibited small changes in K m and k cat , while the S224D mutant yielded 20- to 40-fold increased values for K m and >10-fold decreases in k cat when using the penicillins as substrates.
All crystallographically characterized metallo-β-lactamases have a flexible amino acid chain that extends over the active site [ 37 42 44 45 46 47 48 49 ] . Previous NMR studies on CcrA have shown that this loop "clamps down" on substrate or inhibitor upon binding, and there is speculation that the distortion of substrate upon clamping down of the loop may drive catalysis [ 50 ] . The crystal structure of L1 showed that there is a large loop that extends over the active site, and modeling studies have predicted that two residues, Ile164 and Phe158, make significant contacts with large, hydrophobic substituents at the 2' or 6' positions on penicillins, cephalosporins, or carbapenems [ 37 ] . To test this prediction, Ile 164 and Phe158 were changed from large, hydrophobic residues to alanines to afford the I164A and F158A mutants.
These bacteria become resistant by a number of mechanisms, such as producing enzymes that hydrolyze or inactivate the antibiotics, producing efflux pumps that transport the antibiotic out of the cell, or modifying their cell wall components so they no longer bind effectively to the antibiotics [ 1 2 3 ] . The most common, least expensive, and effective antibiotics are the β-lactam containing antibiotics, such as the penicillins, cephalosporins, and carbapenems [ 2 4 5 ] . These antibiotics are mechanism-based inhibitors of transpeptidase, a bacterial enzyme required for the production of a strong viable cell wall [ 6 7 ] . In response to the widespread use of β-lactam containing antibiotics, bacteria have acquired the ability to produce β-lactamases, which are enzymes that hydrolyze and inactivate β-lactam containing antibiotics.
As with the I164A mutant, the changes in K m and k cat for the penicillins and carbapenems were relatively small, as compared with the values obtained with the cephalosporins (Table 4).
Beta-lactamases have been widely investigated for their role in the metabolism of antibiotics including cephalosporins and penicillins.
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