Penicillinase

Part of speech: noun

Definitions

1. An enzyme produced by certain bacteria that breaks down penicillin antibiotics, rendering them ineffective and causing resistance to treatment
2. A bacterial enzyme capable of deactivating penicillin by hydrolyzing its beta-lactam ring, leading to antibiotic resistance in microorganisms
3. A protein produced by some bacteria which inactivates penicillin antibiotics through chemical modification, preventing the drug from killing the bacteria

Etymology: Penicillinase is a word built from two parts that were each coined for a different purpose. "Penicillin" comes from "Penicillium", the genus name of the mould that produces the antibiotic, and the suffix "-ase" is the standard chemists' marker for an enzyme, as in "amylase" or "lipase". Put together, the name means simply an enzyme that acts on penicillin. The enzyme itself was a discovery about bacteria fighting back. Once penicillin was in clinical use, some bacteria were found to produce a substance that broke the antibiotic's molecular ring apart, rendering it harmless. The name therefore records a defence rather than a product: a microbe's chemical counterattack, labelled with the vocabulary of the drug it defeats.

Synonyms: beta-lactamase, enzyme