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The other type of beta-lactamase is of the metallo type ("type B"). Metallo-beta-lactamases (MBLs) need metal ion(s) (1 or 2 Zn 2+ ions [2]) on their active site for their catalytic activities. [3] The structure of the New Delhi metallo-beta-lactamase 1 is given by 6C89. It resembles a RNase Z, from which it is thought to have evolved.
Similarly, it has been demonstrated that zinc chelators can inhibit the hydrolytic activity of metallo-β-lactamases against β-lactam antibiotics, restoring the activity of the latter. [6] Metallo-beta-lactamases are important enzymes because they are involved in the breakdown of antibiotics by antibiotic-resistant bacteria. [7]
The NDM-1 enzyme is one of the class B metallo-beta-lactamase; other types of carbapenemase are class A or class D beta-lactamases. [11] (The class A Klebsiella pneumoniae carbapenemase is currently the most common carbapenemase, which was first detected in North Carolina, United States, in 1996 and has since spread worldwide. [12]
A lactam is a cyclic amide, and beta-lactams are named so because the nitrogen atom is attached to the β-carbon atom relative to the carbonyl. The simplest β-lactam possible is 2-azetidinone. β-lactams are significant structural units of medicines as manifested in many β-lactam antibiotics . [ 2 ]
An example of such an enzyme is New Delhi metallo-beta-lactamase 1, discovered in 2009.) The genes encoding these enzymes may be inherently present on the bacterial chromosome or may be acquired via plasmid transfer (plasmid-mediated resistance), and β-lactamase gene expression may be induced by exposure to β-lactams. [citation needed]
The structure of the active site in carbonic anhydrases is well known from a number of crystal structures. It consists of a zinc ion coordinated by three imidazole nitrogen atoms from three histidine units. The fourth coordination site is occupied by a water molecule. The coordination sphere of the zinc ion is approximately tetrahedral.
All-β proteins are a class of structural domains in which the secondary structure is composed entirely of β-sheets, with the possible exception of a few isolated α-helices on the periphery. Common examples include the SH3 domain , the beta-propeller domain , the immunoglobulin fold and B3 DNA binding domain .
Beta-Lactamase Inhibitor Proteins (BLIPs) are a family of proteins produced by bacterial species including Streptomyces. BLIP acts as a potent inhibitor of beta-lactamases such as TEM-1 , which is the most widespread resistance enzyme to penicillin antibiotics .