RESUMO
6-Anilinouracils (6-AUs) are dGTP analogues which selectively inhibit the DNA polymerase III of Bacillus subtilis and other Gram-positive bacteria. To enhance the potential of the 6-AUs as antimicrobial agents, a structure-activity relationship was developed involving substitutions of the uracil N3 position in two 6-AU platforms: 6-(3,4-trimethyleneanilino)uracil (TMAU) and 6-(3-ethyl-4-methylanilino)uracil (EMAU). Series of N3-alkyl derivatives of both 6-AUs were synthesized and tested for their ability to inhibit purified B. subtilis DNA polymerase III and the growth of B. subtilis in culture. Alkyl groups ranging in size from ethyl to hexyl enhanced the capacity of both platforms to bind to the polymerase, and with the exception of hexyl, they also significantly enhanced their antimicrobial potency. N3 substitution of the EMAU platform with more hydrophilic hydroxyalkyl and methoxyalkyl groups marginally enhanced anti-polymerase III activity but enhanced antibacterial potency severalfold. In sum, the results of these studies indicate that the ring N3 of 6-anilinouracils can tolerate substituents of considerable size and structural variety and, thus, can be manipulated to significantly enhance the antibacterial potency of this novel class of polymerase III-specific inhibitors.
Assuntos
Antibacterianos/química , Bacillus subtilis/enzimologia , DNA Polimerase III/antagonistas & inibidores , Inibidores Enzimáticos/química , Uracila/análogos & derivados , Antibacterianos/síntese química , Antibacterianos/farmacologia , Bacillus subtilis/efeitos dos fármacos , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/farmacologia , Testes de Sensibilidade Microbiana , Relação Estrutura-Atividade , Uracila/síntese química , Uracila/química , Uracila/farmacologiaRESUMO
Quantitative structure-activity relationships (QSAR) of a series of 6-anilinouracil derivatives were developed for their inhibitory activity against the wild-type DNA polymerase III (pol III) and a mutant enzyme, pol III/azp-12, derived from Bacillus subtilis. Interaction between inhibitors and both enzymes appears to result solely from hydrophobic binding. Comparison of the substituent contributions indicates increased hydrophobic character and a minor change of shape of the inhibitor binding site of the mutant enzyme. Because the two enzymes have identical Km values for substrates, the inhibitor binding site is thought to be distinct from the enzyme active site.
