Murray State University

Poster Title

A New Class of Inhibitors of an Aminoglycoside Antibiotic Kinase

Institution

Murray State University

Abstract

The rise in bacterial resistance to antibiotics has reached a crisis level and is considered a public health emergency. Pathogenic bacteria have countered the overuse of antibiotics by expressing a multitude of gene products that render the drugs ineffective. A family of bacterial enzymes that serves as detoxifying agents of aminoglycoside antibiotics has been identified as ATP-dependent aminoglycoside 3'-phospho-transferases (APH(3')). Along with hydrogen-bonding interactions, these enzymes utilize a pi-pi stacking interaction involving an aromatic amino acid to bind the adenine ring of bound nucleotides. Our results derived from steady-state kinetics and quantum-mechanical calculations suggest that these contacts with the adeninering determine the specificity in the adenine-binding region of these enzymes. Several nucleosides, aromatic, and heteroaromatic compounds, distinct from the adenine ring, have been tested as inhibitors of APH(3')-IIa and APH(3')-IIIa, two of the most prevalent aminoglycoside kinases. Compounds that contain guanine-type ring systems do not block the entry of ATP into the active site of the IIa or IIIa enzyme. 3-amino-5-nitrobenzisothiazole is one of the more potent inhibitors identified to date with an inhibitory constant of 1 μM. Kinetic experiments with four isoquinoline derivatives have also identified potent inhibitors. Although some compounds tested were not potent inhibitors they have provided valuable information on the molecular determinants needed for adenine recognition in the enzyme. Overall, the data suggests that there are strict electrostatic requirements for recognition in the adenine-binding region of these kinases and that contacts may be exploited to design inhibitors of these antibiotic resistance enzymes.

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A New Class of Inhibitors of an Aminoglycoside Antibiotic Kinase

The rise in bacterial resistance to antibiotics has reached a crisis level and is considered a public health emergency. Pathogenic bacteria have countered the overuse of antibiotics by expressing a multitude of gene products that render the drugs ineffective. A family of bacterial enzymes that serves as detoxifying agents of aminoglycoside antibiotics has been identified as ATP-dependent aminoglycoside 3'-phospho-transferases (APH(3')). Along with hydrogen-bonding interactions, these enzymes utilize a pi-pi stacking interaction involving an aromatic amino acid to bind the adenine ring of bound nucleotides. Our results derived from steady-state kinetics and quantum-mechanical calculations suggest that these contacts with the adeninering determine the specificity in the adenine-binding region of these enzymes. Several nucleosides, aromatic, and heteroaromatic compounds, distinct from the adenine ring, have been tested as inhibitors of APH(3')-IIa and APH(3')-IIIa, two of the most prevalent aminoglycoside kinases. Compounds that contain guanine-type ring systems do not block the entry of ATP into the active site of the IIa or IIIa enzyme. 3-amino-5-nitrobenzisothiazole is one of the more potent inhibitors identified to date with an inhibitory constant of 1 μM. Kinetic experiments with four isoquinoline derivatives have also identified potent inhibitors. Although some compounds tested were not potent inhibitors they have provided valuable information on the molecular determinants needed for adenine recognition in the enzyme. Overall, the data suggests that there are strict electrostatic requirements for recognition in the adenine-binding region of these kinases and that contacts may be exploited to design inhibitors of these antibiotic resistance enzymes.