Purification and Properties of Glutamate Kinases Required for l-Proline and l-Glutamine Biosynthesis in Brevibacterium flavum

Abstract

Glutamate kinase activity was separated into two different protein fractions, i.e. glutamate kinase I and II, through the purification of twice carried out ammonium sulfate fractionation and DEAE-cellulose column chromatography, and both specific activities were raised nearly ten times higher. Each kinase was found to catalyze kinase reaction stoichiometrically. The optimum pH range of both kinases was between 7.5 and 8.0. The Km value of kinase I and II for l-glutamatic acid were 1.7 × 10⁻² m and 3.1 × 10⁻² m respectively. Both kinases were specific for only l-glutamic acid, and formed l-glutamine from l-glutamic acid by the addition of ammonium ion instead of NH₂OH. No effect of l-proline on either kinase was detected. l-Glutamine markedly inhibited kinase II competitively with l-glutamic acid. Kinase I catalyzes the so-called forward transfer reaction more effectively than kinase II, whereas kinase II catalyzes the reverse transfer reaction four times effectively. Kinase II seems to be more closely related to l-glutamine biosynthesis and kinase I to l-proline biosynthesis.