Stage-specific differences of a perhaps signal-transferring system in Leishmania donovani

There are stage-specific differences of adenosine 5'-monophosphate (AMP)-catabolizing reactions in amastigote and promastigote Leishmania donovani cells: 1. the pH-optimum of nucleotidase activity is 9.2 in amastigote cells and 5.4 in promastigote cells, 2. adenosine, product of the nucleotidase reaction, is metabolized in a different way: in amastigote cells it is deaminated to inosine while in promastigote cells it is cleaved to adenine. Consequently, hypoxanthine is formed by a cleavage of inosine in amastigote cells and by a deaminating reaction of adenine in promastigote cells. These findings indicate that the rate of the adenylate energy charge and the purine nucleotide synthesis could be regulated stage-specifically. The membrane-bound nucleotidase might serve as a receptor and as the initial link of this sequence of reactions which signalizes an environmental change into the cell.