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.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Acetaldehyde / analogs & derivatives
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Acetaldehyde / metabolism
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Carbohydrate Dehydrogenases / genetics
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Carbohydrate Dehydrogenases / physiology
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Escherichia coli / enzymology
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Escherichia coli / metabolism*
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Escherichia coli Proteins*
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Models, Chemical
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Organophosphates / metabolism*
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Phosphotransferases (Alcohol Group Acceptor) / genetics
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Phosphotransferases (Alcohol Group Acceptor) / physiology
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Pyridoxal Phosphate / analogs & derivatives
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Pyridoxal Phosphate / biosynthesis*
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Pyridoxal Phosphate / metabolism
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Threonine / analogs & derivatives*
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Threonine / metabolism
Substances
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4-phosphothreonine
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Escherichia coli Proteins
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Organophosphates
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hydroxythreonine
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Threonine
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Pyridoxal Phosphate
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Carbohydrate Dehydrogenases
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pdxB protein, E coli
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Phosphotransferases (Alcohol Group Acceptor)
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homoserine kinase
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Acetaldehyde
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pyridoxine 5-phosphate
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glycolaldehyde