Interaction of β-iodopenicillanate with the β-lactamases of Streptomyces albus G and Actinomadura R39

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Abstract
The .beta.-lactamases of S. albus G and Actinomadura R39 are inactivated by .beta.-iodopenicillanate. In contrast with the .beta.-lactamase I from Bacillus cereus, they also efficiently catalyze the hydrolysis of the inactivator; with the S. albus G enzyme, kcat. is larger than 25 s-1 and the number of turnovers before inactivation is 515. With the Actinomadura R39 enzyme, Kcat. is larger than 50 s-1 and the number of turnovers before inactivation is 80. After hydrolysis of the .beta.-lactam amide bone, the product rearranges into 2,3-dihydro-2,2-dimethyl-1,4-thiazine-3,6-dicarboxylate, which exhibits an absorption maximum at 305 nm.