CHARACTERIZATION OF A GLUTAMINE SYNTHETASE-B ACTIVATING (DEADENYLYLATING) ENZYME SYSTEM IN ESCHERICHIA COLI

Biosynthetically inactive labelled glutamine synthetase b was produced by enzymic adenyly‐lation of biosynthetically active glutamine synthetase a with [14C]ATP. Upon incubation of the glutamine synthetase b with a crude extract from E. coli B a reactivation, i. e. an increase of biosynthetic activity, and a release of protein bound radioactivity takes place wth identical kinetics. Thus, E. coli B contains a glutamine synthetase b activating (deadenylylating) enzyme system. The radioactive material released was identified as AMP. Fluoride (2.5 mM) and 2.5 mM ATP stimulate the enzymic activation of glutamine synthetase b multi‐fold. dATP, ITP, GTP, CTP, and UTP also stimulate but AMP inhibits the activation. These effects point to a control of the glutamine synthetase interconverting enzyme system by the ATP/AMP ratio, i. e. by the energy situation of the cell. Copyright © 1969, Wiley Blackwell. All rights reserved