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  • Title: Substitution of aspartic acid-217 of Citrobacter freundii cephalosporinase and properties of the mutant enzymes.
    Author: Tsukamoto K, Kikura R, Ohno R, Sawai T.
    Journal: FEBS Lett; 1990 May 21; 264(2):211-4. PubMed ID: 1972682.
    Abstract:
    On the assumption that Asp-217 of a Citrobacter freundii cephalosporinase forms a salt-bridge with the conserved Lys-67, Asp-217 was changed to glutamic acid, threonine or lysine. The mutant enzymes retained about the same level of activity as that of the wild-type enzyme, and the participation of Asp-217 in the salt-bridge was ruled out. However, the mutations resulted in an increase in hydrolytic activity toward oxyimino-cephalosporins such as cefuroxime, cefmenoxime and ceftazidime, suggesting a possible mechanism of the bacterial resistance to the novel beta-lactams by a single mutation in cephalosporinases.
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