MICROBIAL DEGRADATION OF CEPHALOSPORIN C.

THE antibiotic, cephalosporin C, is closely related to the penicillin family and displays the same mode of action1. Although cephalosporin C possesses the β-lactam ring—the substrate site of penicillinase action—it is resistant to this enzyme and, in fact, acts as a competitive inhibitor. It is, however, attacked by a ‘cephalosporinase’ found in crude preparations of penicillinase from Bacillus cereus2 and by a citrus acetyl esterase3. Although little is known about the site of attack by cephalosporinase, its action causes inactivation of the antibiotic with the loss of 260 mµ absorption and liberation of one acidic group. The esterase converts cephalosporin C to deacetylcephalosporin C, which retains the properties of ultra-violet absorption and resistance to penicillinase but which is a less-active antibiotic. We have now found that these two enzymatic activities are present in many bacteria and actinomycetes but not in the moulds examined.