Bacillus licheniformis penicillinase

Class A comprises a set of enzymes of approximately 30,000 Da that are preferentially active against penicillins and share considerable homology with one another. The key amino-acid residue in members of this class is serine-70. Within this class are the penicillinases of the Gram-positive organisms, Bacillus licheniformis and S. aureus and the TEM-type broad-spectrum y5-lactamases from Gram-negative bacteria. 

It should be appreciated, however, that the enzymes of a functionally similar type may not infrequently be cell-bound in one species of bacterium and in another they may be extracellular—e.g.9 penicillinase and alkaline phosphatase of E. coli are cell-bound, whereas those of Bacillus cereus are extracellular (6). Even in the same strain of bacterium, an enzyme may be partly cell-bound and partially extracellular penicillinase of Bacillus licheniformis is an example (60). Consequently, the above classification is not so distinctive and may change, depending on the circumstances of cells or by their mutation. 

Fig. 7. Induction of penicillinase in Bacillus licheniformis 749 by molybdate (Davies and Collins, unpublished results). =0.5 mM molybdate A = 0- molybdate.

Fig. 8. Postulated model for penicillinase regulation in Bacillus licheniformis.

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