Biosynthesis of vitamin B6: direct identification of the product of the PdxA-catalyzed oxidation of 4-hydroxy-l-threonine-4-phosphate using electrospray ionization mass spectrometry.
PdxA (E.C. 1.1.1.262) catalyzes a key step in the biosynthesis of vitamin B(6): the nicotinamide-dependent oxidation of 4-hydroxy-l-threonine-4-phosphate (HTP) to a product tentatively identified as 3-amino-1-hydroxyacetone 1-phosphate (AHAP). To date, the evidence for the formation of AHAP, while self-consistent, has been largely circumstantial, and does not exclude the possibility that the actual product of the enzyme-catalyzed oxidation of HTP might be 2-amino-3-oxo-4-hydroxybutyric acid 4-phosphate which could undergo rapid, non-enzyme-catalyzed decarboxylation once released from the protein. Use of negative ion electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometric analysis (MS-MS) confirms that AHAP is the product of the PdxA-catalyzed reaction.
Banks
Jerel
J
Department of Chemistry, Box H, Brown University, Providence, Rhode Island, 02912-9108, USA.
Cane
David E
DE
D002384:Catalysis; D029968:Escherichia coli Proteins / Q000032:analysis* / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000032:analysis* / Q000378:metabolism; D010769:Phosphothreonine / Q000032:analysis* / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D025101:Vitamin B 6 / Q000032:analysis* / Q000096:biosynthesis*
D029968:Escherichia coli Proteins; D010769:Phosphothreonine; C060787:pdxA protein, E coli; D025101:Vitamin B 6; D010088:Oxidoreductases