Glutamine synthetase from Acetobacter diazotrophicus: properties and regulation

Glutamine synthetase from Acetobacter diazotrophicus, an endophyte original ly isolated from sugarcane, was studied as a step in the identification of mechanisms underlying the role of A. diazotrophicus as a major supplier of fixed nitrogen to its host plant. The enzyme was purified and partially cha racterized. It was also shown that the enzyme is regulated by adenylylation in response to the nitrogen source. Interestingly, there is no upregulatio n of the synthesis of the enzyme under diazotrophic conditions, which is in contrast to the situation in enterics, e.g. Klebsiella pneumoniae. (C) 200 1 Federation of European Microbiological Societies. Published by Elsevier S cience B.V. All rights reserved.