Threonine Deaminase from Bacillus subtilis II. THE STEADY STATE KINETIC PROPERTIES

摘要: Abstract Threonine deaminase (l-threonine hydro-lyase (deaminating), EC 4.2.1.16) from Bacillus subtilis catalyzes the deamination of threonine at a constant rate upon addition substrate. In presence isoleucine, reaction begins slowly and increases to steady state, inhibited rate. Essentially same state is observed when amount isoleucine added enzyme already catalyzing but achieved slowly. absence inhibitor, substrate saturation curve described by hyperbola. curves are sigmoid can be fitted method Cleland an equation containing S2 terms. Isoleucine was shown competitive-type inhibitor. The kinetic data also versions equations which describe allosteric model Monod, Wyman, Changeux for regulatory proteins. Valine antagonized inhibition in competitive fashion. It did not activate rather, it exerted weak (15%) noncompetitive.