Serine oligopeptidases of trypanosomatids are emerging as important virulence factors and therapeutic targets in trypanosome infections. A major signaling pathway regulating cell invasion by T. cruzi involves mobilization of Ca(2+) from intracellular stores and requires the activity of oligopeptidase B. Oligopeptidase B of L. major was annotated by the genome L. major Friedlin project under accession number Q9XYH4.  A complete open reading frame of Oligopeptidase B was amplified from L. major (LV 39 strain) genomic DNA using forward primer-1 (5' CAT ATG TCG TCG GAC AGC TCC GTC GCG) and reverse primer-2 (5' CTC GAG CTA CTC GAG CTA TTA CCT GCG AAC CAG CAG GCG CAC) designed from L. major Oligopeptidase B sequence (Q9XYH4) using 69^o C of annealing temperature in PCR reaction.   Using the same conditions against genomic DNA of L. amazonensis, L. braziliensis and L. chagasi amplification was not observed. However, using PCR gradient, we amplified an oligopeptidase from Leishmania amazonensis. PCR products of L. major and L. amazonensis were cloned into P-Gem T easy vector (Promega) and sequenced. For L. amazonensis, an ORF of 2.1 Kb coding for a protein of 731 aa with a predicted molecular mass of 82 kDa was identified. The encoded protein of L. amazonensis shares 92% identity to oligopeptidase of L. major and 85% identity to oligopeptidase of T. cruzi. Gene copy number was determined by southern blot analysis in chromosome from promastigotes of L. major (LV 39 strain) and L. amazonensis (PH8 strain). Results suggested that there is more than one oligopeptidase related gene in the L. major and L. amazonensis genome.  In order to estimate the expression level of oligopeptidase in promastigote (methaciclic and prociclic) and amastigote stages by RT-PCR. We extracted mRNA from L. major and L. amazonensis promastigotes (procyclic and metacyclic) and amastigotes by Trizol Reagent (Invitrogen) and synthezed of cDNA with SuperScript Indirect cDNA Labeling Kit (Invitrogen).  The results showed that oligopeptidase is solely expressed in promastigote stage suggesting the role of oligopeptidase B in host infection. Now, we are engaged in protein expression to further biochemical characterization.