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Inhibition of the synthesis of the TEM-type beta-lactamase by purine derivatives.

The beta-lactamase TEM-1 was purified from an Escherichia coli ATCC 11 775 R+TEM culture by preparative isoelectric focussing. This preparation was used to establish a calibration curve between the concentration of the enzyme and the cleavage of nitrocefin, by which the quantitative production of beta-lactamase TEM-1 in the growing culture was determined. The effect of purine derivatives on the synthesis of the beta-lactamase during the growth of the bacterium was tested in order to determine the essential basic structure of the molecule. It is suggested that the keto-methylamino part of the pyrimidine nucleus is decisive for the potency of the structure. Inhibition studies on the purified enzyme demonstrated that the purine compounds act by inhibiting the synthesis of the beta-lactamase and not by inactivation of the enzyme. This mode of action manifests itself as a synergism with amoxycillin against the beta-lactamase producing strain.