Beta-lactamases are enzymes produced by some bacteria and are responsible for their resistance to beta-lactam antibiotics like penicillins, cephamycins, and carbapenems. The lactamase enzyme breaks the β-lactam ring open and deactivates the molecule's antibacterial properties because of a common element in these antibiotics molecular structure: a four-atom ring known as a beta-lactam. TEM-1 is the most commonly-encountered beta-lactamase in gram-negative bacteria. Up to 90 % of ampicillin resistance in E. coli is due to the production of TEM-1. Also responsible for the ampicillin and penicillin resistance that is seen in H. influenzae and N. gonorrhoeae in increasing numbers. Based upon different combinations of changes, currently 140 TEM-type enzymes have been described. Recombinant beta-lactamase TEM-1 contains 264 amino acids residues.