Biosynthetic l-Threonine Deaminase as the Origin of l-Serine Sensitivity of Escherichia coli

L-serine deaminase of Escherichia coli.

The native l-serine deaminase (l-serine hydrolyase, deaminating, EC 4.2.1.13) of Escherichia coli K-12, which seems to be a very labile protein, is rather stable in concentrated solution. Dilution rapidly inactivates it, but in the presence of a saturating concentration of l-serine the molecule is protected from inactivation. It is a very specific enzyme; l-serine is the sole substrate with a K...

The feedback control mechanisms of biosynthetic L-threonine deaminase by L-isoleucine.

Chemotaxis of Escherichia coli to L-serine.

A novel experimental technique was used to quantify the motion of E. coli to varying serine concentrations and gradients so as to capture the spatial and temporal variation of the chemotactic response. The average run speed and the cell diffusivity are found to be dependent on the serine concentration. The measured diffusivities were in the range of 1.2-2.5 x 10 (-10) m(2) s(-1). The study reve...

Energetics of cooperative ligand binding to the active sites of biosynthetic threonine deaminase from Escherichia coli.

The sigmoidal kinetics of alpha-ketobutyrate production catalyzed by threonine deaminase are shifted in the presence of the feedback inhibitor isoleucine and the activator valine to control carbon flow through branched-chain amino acid biosynthesis in Escherichia coli. As an initial effort toward developing a molecular mechanism for cooperativity and feedback inhibition in this enzyme, the bind...

Cooperative binding of the feedback modifiers isoleucine and valine to biosynthetic threonine deaminase from Escherichia coli.

Control of the regulatory enzyme threonine deaminase from Escherichia coli is achieved by isoleucine inhibition and valine activation. The mechanism by which these heterotropic effectors regulate the enzyme was investigated by measuring the binding of isoleucine and valine by spectroscopic, kinetic, calorimetric and equilibrium dialysis techniques. The addition of isoleucine or valine to threon...