L-alanine dehydrogenase from Bacillus subtilis exhibits allosteric kinetic properties in the presence of Zn2+. Zn2+ induces the binding of substrate (L-alanine) to be cooperative at pH 8.0. The effect of pH variation between pH 7.0 and pH 10.0 on the inhibition by Zn2+ correlates with the pH effect on the Km values for L-alanine within these pH range indicating that Zn2+ and substrate compete for the same site. No such cooperativity is induced by Zn2+ when the reaction is carried out at pH 10. At this higher pH, Zn2+ binds with the enzyme with lower affinity and noncompetitive with respect to L-alanine. Inhibition of L-alanine dehydrogenase by Zn2+ depends on the ionic strength. Increase in KCl concentation reduced the inhibition, but allosteric property in Zn2+ binding is conserved. A model for the regulatory mechanism of L-alanine dehydrogenase as a noncooperative substrate-cooperative cofactor allosteric enzyme, which is compatible in both concerted and the sequential allosteric mechanism, is proposed.
|Original language||English (US)|
|Number of pages||5|
|Journal||Bulletin of the Korean Chemical Society|
|State||Published - Dec 20 2000|