PMID:3900058
| Citation |
Ida, N and Tokushige, M (1985) L-Aspartate-induced activation of aspartase. J. Biochem. 98:35-9 |
|---|---|
| Abstract |
During the catalysis of the fumarate amination reaction, aspartase was markedly activated by the product, L-aspartate, as shown by a steep increase in the reaction rate. When NH4+ was replaced by NH2OH, the hydroxylamination reaction proceeded without any acceleration, and was activated upon addition of L-aspartate. The activation required the Mg2+ ion and the alkaline pH, and the half-saturation concentration of L-aspartate for activation was as low as 0.07 mM, which was far lower than the Km value for catalysis. Fumarate showed no activating effect in contrast to L-aspartate, and L-aspartate lowered the Km value for fumarate instead of acting as a competitive inhibitor. Besides L-aspartate, alpha-methyl-DL-aspartate exhibited an activating effect without serving as a substrate. These results suggest that the activation is mediated by an indirect action of L-aspartate which is bound to a site distinct from the catalytic site. |
| Links | |
| Keywords |
Ammonia-Lyases/metabolism; Aspartate Ammonia-Lyase/metabolism; Aspartic Acid/metabolism; Enzyme Activation; Escherichia coli/enzymology; Hydrogen-Ion Concentration; Kinetics; Spectrophotometry, Ultraviolet |
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