scholarly journals Multiple Metabolic Roles for the Nonphotosynthetic Plastid of the Green Alga Prototheca wickerhamii

2005 ◽  
Vol 4 (2) ◽  
pp. 253-261 ◽  
Author(s):  
Tudor Borza ◽  
Cristina E. Popescu ◽  
Robert W. Lee
Keyword(s):  
Green Alga ◽  
De Novo ◽  
Living Organism ◽  
Chlorophyll Synthesis ◽  
Metabolic Functions ◽  
De Novo Purine Biosynthesis ◽  
Isoprenoid Metabolism ◽  
Intracellular Parasites ◽  
Prototheca Wickerhamii ◽  
Mg Chelatase

ABSTRACT The presence of plastids in diverse eukaryotic lineages that have lost the capacity for photosynthesis is well documented. The metabolic functions of such organelles, however, are poorly understood except in the case of the apicoplast in the Apicomplexa, a group of intracellular parasites including Plasmodium falciparum, and the plastid of the green alga Helicosporidium sp., a parasite for which the only host-free stage identified in nature so far is represented by cysts. As a first step in the reconstruction of plastid functions in a nonphotosynthetic, predominantly free-living organism, we searched for expressed sequence tags (ESTs) that correspond to nucleus-encoded plastid-targeted polypeptides in the green alga Prototheca wickerhamii. From 3,856 ESTs, we found that 71 unique sequences (235 ESTs) correspond to different nucleus-encoded putatively plastid-targeted polypeptides. The identified proteins predict that carbohydrate, amino acid, lipid, tetrapyrrole, and isoprenoid metabolism as well as de novo purine biosynthesis and oxidoreductive processes take place in the plastid of P. wickerhamii. Mg-protoporphyrin accumulation and, therefore, plastid-to-nucleus signaling might also occur in this nonphotosynthetic organism, as we identified a transcript which encodes subunit I of Mg-chelatase, the enzyme which catalyzes the first committed step in chlorophyll synthesis. Our data indicate a far more complex metabolism in P. wickerhamii's plastid compared with the metabolic pathways predicted to be located in the apicoplast of P. falciparum and the plastid of Helicosporidium sp.

scholarly journals Carbocyclic substrates for de novo purine biosynthesis.

1991 ◽  
Vol 266 (25) ◽  
pp. 16699-16702
Author(s):  
D.S. Liu ◽  
C.A. Caperelli
Keyword(s):  
De Novo ◽  
Purine Biosynthesis ◽  
De Novo Purine Biosynthesis

scholarly journals Toxoplasma LIPIN is essential in channeling host lipid fluxes through membrane biogenesis and lipid storage

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sheena Dass ◽  
Serena Shunmugam ◽  
Laurence Berry ◽  
Christophe-Sebastien Arnold ◽  
Nicholas J. Katris ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Phosphatidic Acid ◽  
De Novo ◽  
Lipid Synthesis ◽  
Parasite Development ◽  
Membrane Biogenesis ◽  
Membrane Phospholipids ◽  
Phosphatidic Acid Phosphatase ◽  
Intracellular Parasites ◽  
Parasite Survival

AbstractApicomplexa are obligate intracellular parasites responsible for major human diseases. Their intracellular survival relies on intense lipid synthesis, which fuels membrane biogenesis. Parasite lipids are generated as an essential combination of fatty acids scavenged from the host and de novo synthesized within the parasite apicoplast. The molecular and metabolic mechanisms allowing regulation and channeling of these fatty acid fluxes for intracellular parasite survival are currently unknown. Here, we identify an essential phosphatidic acid phosphatase in Toxoplasma gondii, TgLIPIN, as the central metabolic nexus responsible for controlled lipid synthesis sustaining parasite development. Lipidomics reveal that TgLIPIN controls the synthesis of diacylglycerol and levels of phosphatidic acid that regulates the fine balance of lipids between storage and membrane biogenesis. Using fluxomic approaches, we uncover the first parasite host-scavenged lipidome and show that TgLIPIN prevents parasite death by ‘lipotoxicity’ through effective channeling of host-scavenged fatty acids to storage triacylglycerols and membrane phospholipids.

Purine metabolism in Neisseria gonorrhoeae: the requirement for hypoxanthine

1980 ◽  
Vol 26 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Stephen A. Morse ◽  
Lynne Bartenstein
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Growth Medium ◽  
De Novo ◽  
Defined Medium ◽  
Purine Metabolism ◽  
Purine Biosynthesis ◽  
Free Medium ◽  
De Novo Purine Biosynthesis ◽  
Reduced Rate

Strains isolated from disseminated gonococcal infections often require hypoxanthine for growth. The biochemical bases for the requirement for hypoxanthine in strains isolated from both disseminated (Ile−Val−Arg−Hyx−Ura−phenotype) and non-disseminated (Hyx−phenotype) infections were compared. The requirement for hypoxanthine was dependent upon the composition of the growth medium. In a complete defined medium, hypoxanthine was replaced by a mixture of adenine and guanine but not by either purine alone. The addition of adenine alone inhibited gonococcal growth. This inhibition was reversed by the addition of guanine and most likely resulted from an inhibition of de novo purine biosynthesis. In a histidine-free medium, adenine replaced the hypoxanthine requirement in Ile−Val−Arg−Hyx−Ura− strains. Adenine did not replace the hypoxanthine requirement in Hyx− strains. The Ile−Val−Arg−Hyx−Ura− strains exhibited a markedly reduced rate of de novo purine biosynthesis while Hyx− strains were blocked in this pathway. In vivo concentrations of purines are important factors which may limit the intracellular or extracellular growth of these strains.

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