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Comparative Biochemical and Immunological Studies of Bacterial Glutamine Synthetases

^a Laboratory of Biochemistry, National Heart and Lung Institute, National Institutes of Health, Bethesda, Maryland 20014

ABSTRACT

Antisera prepared against adenylylated and unadenylylated Escherichia coli glutamine synthetase cross-reacted with the glutamine synthetases from a number of gram-negative bacteria and one gram-variable species as demonstrated by immunodiffusion and inhibition of enzyme activity. In contrast, the antisera did not cross-react with the glutamine synthetases from gram-positive bacteria (with one exception) nor with the synthetases of higher organisms. Modification of the various glutamine synthetases by covalent attachment of adenosine 5'-monophosphate (or other nucleotides) was tested for by determining whether or not snake venom phosphodiesterase altered catalytic activity in a manner similar to its effect on adenylylated E. coli glutamine synthetase. Only the activity of the glutamine synthetases from gram-negative bacteria grown with specific levels of nitrogen sources could be altered by snake venom phosphodiesterase. In addition, a relative order of antigenic homology between cross-reacting enzymes was suggested based on the patterns of spur formation in the immunodiffusion assay.

¹ Present address: Viral Carcinogenesis Branch, National Cancer Institute, National Institutes of Health, Bethesda, Md. 20014.

² Present address: Microbial Physiology Section, Laboratory of Microbiology and Immunology, National Institute of Dental Research, National Institutes of Health, Bethesda, Md. 20014.