Cofactor Requirements for Dehalogenation of 4-Halobenzoic Acids by Acinetobacter sp. Strain ST-1

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Unlike intact cells, cell extracts from a degrader of 4-chlorobenzoic acid (4-CBA), Acinetobacter sp. strain ST-1, could not dehalogenate 4-CBA. When both ATP and coenzyme A (CoA) were added, the extracts dehalogenated 4-CBA. When one of these cofactors was omitted, dehalogenation activity was not detected. The addition of the divalent metal ions Mg²⁺, Mn²⁺, Zn²⁺, or Co²⁺ increased the amount of reaction product from 2.5- to 3-fold; Fe²⁺ or Cu²⁺, however, inhibited dehalogenation. When ATP, CoA, and Mg²⁺ were added to the assay mixture, 4-CBA was converted hydrolytically to 4-hydroxybenzoic acid in 91% yield. Stoichiometric results suggested that CoA might function in the dehalogenation of 4-CBA by strain ST-1 as a real coenzyme that forms an intermediate of the CoA thioester of 4-CBA. The requirement for the molar ratio of ATP to 4-CBA to be 2 or more might be related to the energy requirement for the formation of the CoA thioester. These findings suggest that a process for the dehalogenation by strain ST-1 of 4-CBA and its analogs 4-bromobenzoic and 4-iodobenzoic acid involves the intermediate formation of a CoA thioester, activating hydrolytic dehalogenation.