An example would be the bacteria that secrete penicillinase, which is an enzyme that destroys penicillin.    From Wordnik.com.  [Cities In Flight]

Recall that Axe did not work with the native TEM-1 penicillinase, but rather with a variant that had a lower activity.    From Wordnik.com.  [Axe (2004) and the evolution of enzyme function - The Panda's Thumb] Reference

Antibacterial (antibiotic) of the penicillin group, acting specifically against penicillinase producing staphylococci.    From Wordnik.com.  [Chapter 4] Reference

Therefore it is necessary to treat breast infections with a penicillinase-resistant antibiotic such as either flucloxacillin or erythromycin.    From Wordnik.com.  [Chapter 39] Reference

The object of interest was the so-called large domain of the TEM-1 penicillinase, an enzyme that breaks down antibiotics related to penicillin.    From Wordnik.com.  [Axe (2004) and the evolution of enzyme function - The Panda's Thumb] Reference

C. Resistance to penicillin is mediated both by plasmid-encoded penicillinase and by changes in chromosome-encoded proteins that control the permeability of the drug.    From Wordnik.com.  [Recently Uploaded Slideshows] Reference

Staphylococcus aureus (MRSA), resulting in the concept that MRSA has emerged on a few occasions after penicillinase-stable β-lactam antibiotics were introduced to clinical practice, followed by intercontinental spread of individual clones.    From Wordnik.com.  [Proceedings of the National Academy of Sciences current issue] Reference

Axe’s numbers tell us about the apparent isolation of the low-activity variant, but reveal little nor can it be expected to about the “isolation” or evolution of TEM-1 penicillinase.    From Wordnik.com.  [Axe (2004) and the evolution of enzyme function - The Panda's Thumb] Reference

Before I discovered I wasn't cut out to be a bench biochemist, my undergraduate research was on "Competitive inhibition of penicillinase by notalysin, a.    From Wordnik.com.  [Citizendium, the Citizens' Compendium - Recent changes [en]] Reference