The streptococcolytic enzyme zoocin A is a penicillin-binding protein

Abstract

Zoocin A is a streptococcolytic enzyme produced by Streptococcus equi subsp. zooepidemicus 4881 that has an unknown site of action on the peptidoglycans of susceptible organisms. Analysis of a mutant strain in which the genes for zoocin A and resistance to zoocin A were inactivated revealed that this strain was more susceptible to β-lactam antibiotics than the parental organism. Purified zoocin A had weak β-lactamase activity, bound radioactive penicillin covalently, and its streptococcolytic activity was inhibited by penicillin. Thus, zoocin A is a penicillin-binding protein and presumably is a d-alanyl endopeptidase.