ABSTRACT
Polyamines, in particular spermidine (Sp), and the tripeptide glutathione (GSH) are predominant metabolites in almost all organisms. The polycationic and aliphatic nature of polyamines favor their interaction with several macromolecules and, hence, their involvement in a plethora of fundamental cellular events such as transcription, translation, regulation of enzyme activity, differentiation, and proliferation. Although glutathionylspermidine derivatives play both common and different biological roles in Enterobacteria and kinetoplastid organisms, a distinctive feature is that they are not indispensable for the prokaryotes but for many trypanosomatids. The amino acid identity between bacterial and Euglenida or Kinetoplastida glutathionyl spermidine synthetase/amidase (GspS) is low, which contrasts with the higher degree of sequence conservation among Euglenida and Kinetoplastida GspS. With a thiol-redox metabolism fully sustained by trypanothione, there was no selective pressure left to express a GspS gene, which was consequently lost or silenced in some Kinetoplastida.
