TEM-89 beta-lactamase produced by a Proteus mirabilis clinical isolate: new complex mutant (CMT 3) with mutations in both TEM-59 (IRT-17) and TEM-3.

TEM-89 (CMT-3) is the first complex mutant beta-lactamase produced by a clinical strain of Proteus mirabilis (strain Pm 631). This new enzyme, which has a pI of 6.28, is derived from TEM-3 and has a single amino acid substitution also encountered in TEM-59 (inhibitor-resistant TEM beta-lactamase IRT-17): Ser-130 to Gly. TEM-89 hydrolyzed penicillins to the same extent that TEM-3 did but lost almost all hydrolytic activity for cephalosporins and, like TEM-59, was highly resistant to inhibitors.