Transsulfuration is an active pathway for cysteine biosynthesis in Trypanosoma rangeli.
BACKGROUND
Cysteine, a sulfur-containing amino acid, plays an important role in a variety of cellular functions such as protein biosynthesis, methylation, and polyamine and glutathione syntheses. In trypanosomatids, glutathione is conjugated with spermidine to form the specific antioxidant thiol trypanothione (T[SH]2) that plays a central role in maintaining intracellular redox homeostasis and providing defence against oxidative stress.


METHODS
We cloned and characterised genes coding for a cystathionine β-synthase (CβS) and cysteine synthase (CS), key enzymes of the transsulfuration and assimilatory pathways, respectively, from the hemoflagellate protozoan parasite Trypanosoma rangeli.


RESULTS
Our results show that T. rangeli CβS (TrCβS), similar to its homologs in T. cruzi, contains the catalytic domain essential for enzymatic activity. Unlike the enzymes in bacteria, plants, and other parasites, T. rangeli CS lacks two of the four lysine residues (Lys26 and Lys184) required for activity. Enzymatic studies using T. rangeli extracts confirmed the absence of CS activity but confirmed the expression of an active CβS. Moreover, CβS biochemical assays revealed that the T. rangeli CβS enzyme also has serine sulfhydrylase activity.


CONCLUSIONS
These findings demonstrate that the RTS pathway is active in T. rangeli, suggesting that this may be the only pathway for cysteine biosynthesis in this parasite. In this sense, the RTS pathway appears to have an important functional role during the insect stage of the life cycle of this protozoan parasite.
Laboratórios de Protozoologia e de Bioinformática, Departamento de Microbiologia, Imunologia e Parasitologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC 88040-970, Brasil. ibicris@gmail.com.
Ibeth
I
Romero
Jair
J
Téllez
Lais Eiko
LE
Yamanaka
Mario
M
Steindel
Alvaro José
AJ
Romanha
Edmundo Carlos
EC
Grisard
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D003541:Cystathionine beta-Synthase / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000096:biosynthesis*; D003547:Cysteine Synthase / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010714:Phosphatidylethanolamines; D013045:Species Specificity; D014349:Trypanosoma cruzi / Q000201:enzymology; D057509:Trypanosoma rangeli / Q000201:enzymology*
D010714:Phosphatidylethanolamines; C049381:1,2-bis(decanoylthio)-1,2-dideoxyglycerol-3-phosphorylethanolamine; D003547:Cysteine Synthase; D003541:Cystathionine beta-Synthase; D003545:Cysteine