LOSS OF INDIVIDUAL ELECTROSTATIC INTERACTIONS BETWEEN AMINOGLYCOSIDE ANTIBIOTICS AND RESISTANCE ENZYMES AS AN EFFECTIVE MEANS TO OVERCOMING BACTERIAL DRUG-RESISTANCE

Aminoglycoside-modifying enzymes modify the structures of aminoglycoside antibiotics, rendering them ineffective, a process which confers resistance to the antibiotic. Electrostatic interactions (ion pairing and hydrogen bonding) are believed to be significant for both substrate recognition and catalysis by these enzymes. Regiospecific syntheses of seven distinct deaminated analogues of neamine and kanamycin A, two aminoglycoside antibiotics, are described. Each of these compounds would have impaired interaction with a different subsite of the enzyme active sites. All seven molecules were shown to be exceedingly poor substrates for two aminoglycoside-modifying enzymes, aminoglycoside 3'-phosphotransferases types Ia and IIa. The energetic contribution of interactions of the active-site functions with each of these amines on stabilization of the transition-state species has been evaluated to be in the range of 6-11 kcal/mol, the largest energy contribution recorded in the literature for such interactions. The biological activities of these analogues were the same against the resistant organisms harboring aminoglycoside 3'-phosphotransferases types Ia and IIa as those against the background strain without the resistant enzymes. Thus, these compounds are virtually unmodified by those enzymes in vivo. The principles described here should be of general interest for circumvention of resistance to other antibiotics, by redesigning the electrostatic interactions with their corresponding resistance enzymes.