An integrated study of threonine-pathway enzyme kinetics in Escherichia coli.
We have determined the kinetic parameters of the individual steps of the threonine pathway from aspartate in Escherichia coli under a single set of experimental conditions chosen to be physiologically relevant. Our aim was to summarize the kinetic behaviour of each enzyme in a single tractable equation that takes into account the effect of the products as competitive inhibitors of the substrates in the forward reaction and also, when appropriate (e.g. near-equilibrium reactions), as substrates of the reverse reactions. Co-operative feedback inhibition by threonine and lysine was also included as necessary. We derived the simplest rate equations that describe the salient features of the enzymes in the physiological range of metabolite concentrations in order to incorporate them ultimately into a complete model of the threonine pathway, able to predict quantitatively the behaviour of the pathway under natural or engineered conditions.
Chassagnole
C
C
INSERM EMI 9929, University Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux, France.
Raïs
B
B
Quentin
E
E
Fell
D A
DA
Mazat
J P
JP
D001222:Aspartate Kinase / Q000378:metabolism; D001223:Aspartate-Semialdehyde Dehydrogenase / Q000378:metabolism; D019757:Carbon-Oxygen Lyases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism*; D006715:Homoserine Dehydrogenase / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D013912:Threonine / Q000378:metabolism*
D007527:Isoenzymes; D013912:Threonine; D006715:Homoserine Dehydrogenase; D001223:Aspartate-Semialdehyde Dehydrogenase; D017853:Phosphotransferases (Alcohol Group Acceptor); C021370:homoserine kinase; D001222:Aspartate Kinase; D019757:Carbon-Oxygen Lyases; C023160:threonine synthase