Origin and function of penicillinase: a problem in biochemical evolution.

The title of this lecture is intentionally provocative. It is well known that there are many varieties of the enzyme that can split the /3-lactam bond of penicillins and/or cephalosporins (Fig. 1)-the specific reaction referred to generally as "peni-cillinase." And their physiological role in the life history of the bacteria which produce them is still a matter of controversy. But the case I wish to argue will be one in favour both of recognizing the relation between the various "brands" of the enzyme, despite many striking chemical differences, and of considering the possibility of a common or similar evolutionary origin.