Affiliation:
1. Rickettsial Diseases Section, Laboratory of Microbial Structure and Function, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, Montana 59840
2. Naval Medical Research Institute, Bethesda, Maryland 20014
Abstract
Adenosine 5′-triphosphate (ATP) was catabolized by whole cells and cell-free extracts of
Rickettsia typhi
to adenosine 5′-diphosphate (ADP) and then to adenosine 5′-monophosphate (AMP), the end product of ATP catabolism under the experimental conditions used. The only intermediate of the pathway from ATP to AMP which was identified by thin-layer chromatography and quantitated by the
14
C content was ADP, whereas products such as adenine, adenosine, hypoxanthine, inosine, and inosine 5′-monophosphate were not detected. The enzymes which could be theoretically responsible for the catabolism or the anabolism of AMP were not detected by standard assay procedures. Most importantly, 5′-nucleotidase or nonspecific phosphatase and AMP nucleosidase activities were undetectable under a variety of experimental conditions. Although these two enzymes remove AMP from the adenylate pool in other cells, they are apparently nonfunctional in
R. typhi
. The biosynthesis of ATP was initiated by adenylate kinase because no adenine phosphoribosyltransferase or adenosine kinase could be detected. Furthermore, AMP was transported intact without prior dephosphorylation. These observations suggest that for
R. typhi
the in vivo activity of adenine nucleotide interconversion was limited to the nucleotides, with AMP being the end product of ATP catabolism, and that the salvage of purine bases and nucleosides was not an essential feature of purine metabolism. These results elucidate the findings of a previous study which showed that in the absence of glutamate as a source of energy, the adenylate energy charge of resting cells of
R. typhi
is drastically lowered by the high proportion of AMP.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
9 articles.
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