title: 4-Phospho-hydroxy-L-threonine is an obligatory intermediate in pyridoxal 5'-phosphate coenzyme biosynthesis in Escherichia coli K-12.
abstract: We show that thrB-encoded homoserine kinase is required for growth of Escherichia coli K-12 pdxB mutants on minimal glucose medium supplemented with 4-hydroxy-L-threonine (synonym, 3-hydroxyhomoserine) or D-glycolaldehyde. This result is consistent with a model in which 4-phospho-hydroxy-L-threonine (synonym, 3-hydroxyhomoserine phosphate), rather than 4-hydroxy-L-threonine, is an obligatory intermediate in pyridoxal 5'-phosphate biosynthesis. Ring closure using 4-phospho-hydroxy-L-threonine as a substrate would lead to formation of pyridoxine 5'-phosphate, and not pyridoxine, as the first B6-vitamer synthesized de novo. These considerations suggest that E. coli pyridoxal/pyridoxamine/pyridoxine kinase is not required for the main de novo pathway of pyridoxal 5'-phosphate biosynthesis, and instead plays a role only in the B6-vitamer salvage pathway.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Houston Medical School 77030-1501, USA.
authors.forename: G
authors.initials: G
authors.lastname: Zhao
authors.forename: M E
authors.initials: ME
authors.lastname: Winkler
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives / Q000378:metabolism; D002237:Carbohydrate Dehydrogenases / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D029968:Escherichia coli Proteins; D008956:Models, Chemical; D010755:Organophosphates / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000502:physiology; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000096:biosynthesis* / Q000378:metabolism; D013912:Threonine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C098563:4-phosphothreonine; D029968:Escherichia coli Proteins; D010755:Organophosphates; C011285:hydroxythreonine; D013912:Threonine; D011732:Pyridoxal Phosphate; D002237:Carbohydrate Dehydrogenases; C061651:pdxB protein, E coli; D017853:Phosphotransferases (Alcohol Group Acceptor); C021370:homoserine kinase; D000079:Acetaldehyde; C024593:pyridoxine 5-phosphate; C010972:glycolaldehyde