Production of a variant of β-lactamase II with selectively decreased cephalosporinase activity by a mutant of Bacillus cereus 569/H/9

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Abstract
Mutants of B. cereus 569/H/9 were screened in a search for strains that synthesize variants of .beta.-lactamase II. One of these mutants (strain 569/H/9/1) produces a .beta.-lactamase II-like enzyme that shows a selective decrease in cephalosporinase activity. .beta.-Lactamase II from strain 569/H/9/1 was purified to apparent homogeneity and its kinetic properties were examined. This enzyme resembles the parent .beta.-lactamase II in its relative activity with benzylpenicillin as substrate when Zn(II) is replaced by other metal ions, but differs detectably from the parent enzyme in its isoelectric point.