TABLE 1.

Inhibition of different bacterial Phe-RS enzymes by the phenyl-thiazolylurea-sulfonamides

Enzyme and compound or drug	IC50 (μM)a
	E. coli	H. influenzaeb	S. pneumoniaeb
Phe-RS
1	0.007	0.02	0.2
2	0.008	0.008	0.2
3	0.015	0.015	0.3
4	0.015	0.015	0.05
5	0.025	0.06	0.04
6	0.02	0.02	0.2
7	<0.005	0.01	0.3
Ile-RS
Mupirocin	0.0014b	0.0014	0.0014

^aIC₅₀s were determined for Phe-RS derived from different gram-negative and gram-positive pathogens. Inhibition of Ile-RS by mupirocin was measured in the presence of [¹⁴C]Ile instead of [¹⁴C]Phe; the results are included for comparison.

^bValues are the results of investigations performed using cell extracts.