Genetic analysis indicates that Escherichia coli possesses two independent pathways for oxidation of phosphite (Pt) to phosphate. One pathway depends on the 14-gene phn operon, which encodes the enzyme C-P lyase. The other pathway depends on the phoA locus, which encodes bacterial alkaline phosphatase (BAP). Transposon mutagenesis studies strongly suggest that BAP is the only enzyme involved in the phoA-dependent pathway. This conclusion is supported by purification and biochemical characterization of the Pt-oxidizing enzyme, which was proven to be BAP by N terminus protein sequencing. Highly purified BAP catalyzed Pt oxidation with specific activities of 62-242 milliunits/mg and phosphate ester hydrolysis with specific activities of 41-61 units/mg. Surprisingly, BAP catalyzes the oxidation of Pt to phosphate and molecular H2. Thus, BAP is a unique Pt-dependent, H2-evolving hydrogenase. This reaction is unprecedented in both P and H biochemistry, and it is likely to involve direct transfer of hydride from the substrate to water-derived protons.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - May 21 2004|
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