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Updated: Aug 11, 2026
Nucleoside Triphosphates - From Synthesis to Biochemical Characterization
Published on: April 3, 2014
Synthesis of deoxyribomononucleotides in Mollicutes: dependence on deoxyribose-1-phosphate and PPi
Abstract:
Cell extracts of Acholeplasma laidlawii B-PG9, Acholeplasma morum S2, Mycoplasma capricolum 14, and Mycoplasma gallisepticum S6 were examined for 37 cytoplasmic enzyme activities involved in the salvage and biosynthesis of purines. All of these organisms had adenine phosphoribosyltransferase activity (EC 2.4.2.7) and hypoxanthine phosphoribosyltransferase activity (EC 2.4.2.8). All of these organisms had purine-nucleoside phosphorylase activity (EC 2.4.2.1) in the synthetic direction using ribose-1-phosphate (R-1-P) or deoxyribose-1-phosphate (dR-1-P); this activity generated ribonucleosides or deoxyribonucleosides, respectively. The pyrimidine nucleobase uracil could also be ribosylated by using either R-1-P or dR-1-P as a donor. The synthesis of deoxyribonucleosides from nucleobases and dR-1-P has been reported from only one other procaryote, Escherichia coli (L. A. Mason and J. O. Lampen, J. Biol. Chem. 193:539-547, 1951). The reverse of this phosphorylase reaction is more widely known, and we found such activity in all mollicutes studied. Some Acholeplasma species but not the Mycoplasma species can phosphorylate deoxyribonucleosides to deoxyribomononucleotides by a PPi-dependent deoxyribonucleoside kinase activity, which was first reported in this group for the ribose analogs (V. V. Tryon and J. D. Pollack, Int. J. Syst. Bacteriol. 35:497-501, 1985). This is the first report of PPi-dependent purine deoxyribonucleoside kinase activity. An ATP-dependent purine deoxyribonucleoside kinase activity is known only in salmon milt extracts (H. L. A. Tarr, Can. J. Biochem. 42:1535-1545, 1964). Deoxyribomononucleotidase activity was also found in cytoplasmic extracts of these mollicutes. This is the first report of deoxyribomononucleotidase activity.
Insights
This study investigated purine metabolism enzymes in mollicutes, finding key salvage and biosynthesis activities. Notably, Acholeplasma species possess unique pyrophosphate-dependent deoxyribonucleoside kinase activity.
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Mollicutes, a unique class of bacteria, lack cell walls and possess minimal genomes.
- Understanding their metabolic pathways, particularly purine salvage and biosynthesis, is crucial for their biology and potential as pathogens.
- Previous studies have identified some enzymes but a comprehensive analysis of purine-related enzyme activities in diverse mollicutes was lacking.
Purpose of the Study:
- To comprehensively examine cytoplasmic enzyme activities involved in purine salvage and biosynthesis across different mollicute species.
- To identify novel enzymatic activities or variations in known pathways within these organisms.
- To compare enzyme profiles between Acholeplasma and Mycoplasma genera.
Main Methods:
- Cell extracts from Acholeplasma laidlawii, Acholeplasma morum, Mycoplasma capricolum, and Mycoplasma gallisepticum were prepared.
- A panel of 37 cytoplasmic enzyme activities related to purine metabolism was assayed.
- Specific enzyme activities, including phosphoribosyltransferases, nucleoside phosphorylases, and deoxyribonucleoside kinases, were characterized.
Main Results:
- All examined mollicutes exhibited adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase activities.
- Purine-nucleoside phosphorylase activity was detected in the synthetic direction in all species.
- A novel pyrophosphate-dependent deoxyribonucleoside kinase activity was identified in Acholeplasma species, alongside deoxyribomononucleotidase activity in all studied mollicutes.
Conclusions:
- Mollicutes possess a functional purine salvage pathway.
- Acholeplasma species demonstrate a unique pyrophosphate-dependent deoxyribonucleoside kinase, distinguishing them from Mycoplasma species.
- The presence of deoxyribomononucleotidase activity suggests further purine metabolism regulation in these organisms.
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