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Is Pneumocystis a plant?
1Department of Biological Sciences, University of Cincinnati, Ohio 45221, USA. Edna.Kaneshiro@uc.edu
The Journal of Eukaryotic Microbiology
|November 12, 2002
Summary
Pneumocystis, an AIDS-associated lung pathogen, uniquely synthesizes sterols by adding one or two methyl groups, unlike fungi. This study details its unusual sterol synthesis pathway, offering insights into this opportunistic pathogen.
Area of Science:
- Biochemistry
- Mycology
- Opportunistic Infections
Background:
- Pneumocystis is an AIDS-associated opportunistic lung pathogen.
- It exhibits unusual biochemical features, notably its sterol composition.
- Unlike fungi, Pneumocystis lacks ergosterol, the major fungal sterol.
Purpose of the Study:
- To investigate the distinct sterols synthesized by Pneumocystis.
- To understand the unusual sterol biosynthesis pathway in P. carinii.
- To compare the P. carinii sterol synthesis with that of fungi, plants, and other organisms.
Main Methods:
- Analysis of sterol composition in P. carinii.
- Enzymatic studies of S-adenosyl-L-methionine:C-24 sterol methyl transferase (SAM:SMT).
- Comparison of P. carinii sterol synthesis with homologous enzymes from other species.
Main Results:
- Pneumocystis synthesizes delta(7) 24-alkysterols, similar to some basidiomycete rust fungi.
- The P. carinii SAM:SMT enzyme can transfer one or two methyl groups, producing C28 and C29 24-alkylsterols.
- P. carinii lacks C-5 and C-22 double bonds in sterols, unlike most fungi and plants.
- The P. carinii SAM:SMT shows unique substrate preference for lanosterol.
- C31 24-Methylenelanosterol and C32 pneumocysterol accumulate in some P. jiroveci populations.
Conclusions:
- Pneumocystis possesses a distinct sterol biosynthesis pathway.
- The P. carinii SAM:SMT enzyme exhibits unique characteristics in methyl group transfer and substrate preference.
- These findings contribute to understanding the unique biology of this opportunistic pathogen.