Enzymes of Glutamate and Glutamine Biosynthesis in Bacillus licheniformis

Abstract

This chapter discusses the purification and characterization of glutamate dehydrogenase, glutamate synthase, and glutamine synthetase and an examination of the pools of ammonia assimilatory metabolites in Bacillus licheniformis . B licheniformis contains an NADP + -specific glutamate dehydrogenase that apparently serves an anabolic function. The enzyme was purified and it was found to be distinct from the glutamate dehydrogenase-like activity of glutamate synthase. The glutamate synthase from B. licheniformis was purified to apparent homogeneity and it showed to be quite similar, in physical properties, to the enzyme from E. coli and K. aerogenes . The glutamine synthetase of B. licheniformis was purified to near homogeneity and shown to be a dodecamer of 616,000 MW. In B. licheniformis , the enzymes of ammonia assimilation appear to serve biosynthetic functions only. The kinetic characteristics of the glutamate synthase and glutamine synthetase appear to be in harmony with their ability to provide relatively high pools of glutamate and glutamine under all growth conditions. Although B. licheniformis cells respond to the nitrogen source in the growth medium by altering growth rates and levels of nitrogen catabolic enzymes, glutamine synthetase does not appear to be involved in the control of these responses.