RECENT DEVELOPMENTS ON THE REGULATION AND STRUCTURE OF GLUTAMINE-SYNTHETASE ENZYMES FROM SELECTED BACTERIAL GROUPS

The structure of glutamine synthetase (GS) enzymes from diverse bacter ial groups fall into three distinct classes. GSI is the typical bacter ial GS, GSII is similar to the eukaryotic GS and is found together wit h GSI in plant symbionts and Streptomyces, while GSIII has been found in two unrelated anaerobic rumen bacteria. In most cases, the structur al gene for GS enzyme is regulated in response to nitrogen. However, d ifferent regulatory mechanisms, to ensure optimal utilization of nitro gen substrates, control the GS enzyme in each class.