Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Three glutamate kinases (GK 1, GK 2 and GK 3) have been found in the leaves of winter wheat (Triticum aestivum L). They were separated by salting out with ammonium sulphate and by chromatography on DEAE-cellulose in a concentration gradient of KCl and on Sephadex G-100. GK 1 belongs to the biosynthesis of L-proline, which inhibits it according to the principle of feedback, GK 2 to the biosynthesis of glutamine; the function of GK 3 has not been found. The partically purified oligomer GK 1 had a molecular weight of 254 000 and dissociated to subunits of molecular weights 84 000 and 42 000. In a K⁺-phosphate buffer, 50 mmol/l, it was active in a pH range of 6.3 to 8.0, with an optimum of 7.2. An amine buffer inhibited it completely. The reaction required Mg²⁺ ions as activators and L-glutamate and ATP as substrates. ATP in a concentration above 70 mmol/l inhibited it. The steady-state kinetics at the optimum pH have shown that GK 1 produces a complex co-operativity of the substrates and belongs to the slowly dissociating hysteretic enzymes of the type N_p P.