A new activity for an old enzyme: Escherichia coli bacterial alkaline phosphatase is a phosphite-dependent hydrogenase.
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.
Yang
Kechao
K
Department of Microbiology, University of Illinois at Urbana-Champaign, B103 Chemical and Life Sciences Laboratory, 601 South Goodwin Avenue, Urbana, IL 61801, USA.
Metcalf
William W
WW
D000469:Alkaline Phosphatase / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D006859:Hydrogen / Q000378:metabolism; D006864:Hydrogenase / Q000378:metabolism*; D006868:Hydrolysis; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D010710:Phosphates / Q000378:metabolism; D017905:Phosphites / Q000378:metabolism*; D011522:Protons
D010710:Phosphates; D017905:Phosphites; D011522:Protons; D006859:Hydrogen; D006864:Hydrogenase; D000469:Alkaline Phosphatase