Dependency on Serine Concentration of the Activity of Tryptophan Synthase. Cooperative Properties

Abstract

The activity of the enzyme trypto-L-Serine binding was found to follow the pattern phan synthase from Escherichia coli was tested as of negative cooperativity both by kinetic and by a function of the concentration of L-serine which equilibrium methods. The enzyme kinetic data serves as a substrate in the indole to tryptophan support the view that a rapid equilibration model reaction as well as for the L -serine deaminase for the enzyme · substrates complex formation is activity.not strictly obeyed. Abhängigkeit der Aktivität der Tryptophan-Synthase von der Sennkonzentration: Cooperative EigenschaftenZusammenfassung: Die Abhängigkeit der Aktivi-negative Cooperativität sowohl in kinetischen Extät des Enzyms Tryptophan-Synthase von der perimenten als auch in Gleichgewichtsdialyse-L -Serin-Konzentration wurde untersucht; L -Serin Versuchen. ist Substrat für dieses Enzym sowohl in der Tryp-Aus den enzymkinetischen Daten läßt sich erkentophansynthese aus Indol als auch in der Serinnen, daß das Enzym nicht strikt einem "rapid Desaminieruilgfcreaktion. Die Serinbindung zeigt equilibration"-Modell folgt.

Characterization of the reaction of L-serine and indole with Escherichia coli tryptophan synthase via rapid-scanning ultraviolet-visible spectroscopy

“…which then is followed by 270 turnover cycles of the active sites (based on a /ccat = 5 s_1 at 25 °C, 26.7 µ ß sites, pH 7.8, and 2 s) (Lane & Kirschner, 1983b). Consequently, on the basis of these findings and in agreement with the work of Heilmann and Bürger (1981), we conclude that L-serine acts both as substrate and as an allosteric effector that influences the distribution of bound species in the steady state.…”

“…Lane and Kirschner (1981) have shown that the binding of either 3'-(indol-3-yl)propyl phosphate or benzimidazole to the a subunits of •ß2 increases the affinity of the ß sites for ligands. The inhibitory and activating effects respectively of high concentrations of indole and L-serine (Lane & Kirschner, 1983b;Kirschner et al, 1975;Heilmann, 1978;Heilmann & Bürger, 1981) provide further indications that ligand-mediated site-site interactions are transmitted across the -ß subunit interface. It therefore is likely that such allosteric effects are responsible both for the inhibition of the reaction of 2ß2 with L-serine by high indole concentrations (viz., Figure 2) and for the spectral changes detected in rt* (viz., Figures 4 and 5).…”