S-adenosylmethionine decarboxylase from Leishmania infantum promastigotes:: molecular cloning and differential expression

S-Adenosylmethionine decarboxylase (Ado-MetDC), an enzyme involved in the synthesis of polyamines as well as in the cell methylation processes, has been considered in trypanosomes as a specific drug target. We have cloned by RT-PCR a DNA fragment of 1,364 by which contains the open reading frame and the 5' end fragment of the AdoMetDC encoding gene from the parasite protozoon Leishmania infantum. The 1,197 by ORF encodes for a 392 amino acid residue polypeptide. The sequence comparison with AdMetDC from different species showed a high level of homology, around 80%, with the American and African trypanosomes and a certain distance from the polypeptides of higher eukaryotes. AdoMetDC has been cloned in a pQE32 vector and overexpressed in a M15 Escherichia coli strain. The gene expression shows variations between the distinct phases of the parasite, being higher in the most infective one. This fact may be related to the multiple defense mechanism of the protozoon against the macrophage action.