PMID:4364023
| Citation |
Théze, J, Kleidman, L and St Girons, I (1974) Homoserine kinase from Escherichia coli K-12: properties, inhibition by L-threonine, and regulation of biosynthesis. J. Bacteriol. 118:577-81 |
|---|---|
| Abstract |
We have partially purified homoserine kinase from a genetically derepressed strain of Escherichia coli K-12. The optimum pH of the enzyme-substrate reaction was 7.8 and the K(m) values for l-homoserine and adenosine 5'-triphosphate were both 3 x 10(-4) M. K(+) (or NH(4) (+)) as well as Mg(2+) were required for its activity. The sedimentation coefficient determined by ultracentrifugation in a sucrose density gradient was 5.0 +/- 0.25S. l-Homoserine was an excellent protector against heat inactivation of homoserine kinase. l-Threonine was a competitive inhibitor of homoserine kinase, suggesting that end-product inhibition of this enzyme plays a role in vivo in the overall regulation of threonine biosynthesis. The specific activity of aspartokinase I-homoserine dehydrogenase I and of homoserine kinase showed a strong positive correlation in extracts from strains under widely varying conditions of genetic or physiological derepression; it was concluded that these two enzymes are coordinately regulated in E. coli K-12. |
| Links | |
| Keywords |
Adenosine Triphosphate/metabolism; Alcohol Oxidoreductases/metabolism; Aspartic Acid; Cell-Free System; Centrifugation, Density Gradient; Enzyme Repression; Escherichia coli/enzymology; Homoserine/metabolism; Hot Temperature; Hydrogen-Ion Concentration; Magnesium/metabolism; Phosphotransferases/antagonists & inhibitors; Phosphotransferases/biosynthesis; Phosphotransferases/metabolism; Stereoisomerism; Threonine/pharmacology |
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