The gene xac2987 from Xanthomonas axonopodis pv citri has been annotated as a proline iminopeptidase. We have cloned this gene and expressed the protein in Escherichia coli in order to characterize it. The protein was purified fused to a histidine tag by IMAC. The protein is a broad range aminopeptidase being able to catalyze the removal of several amino acids from synthetic substrates, it is more active against proline; with more than 50 % activity with serine, glycine and alanine; more than 30 % with histidine and tyrosine; more than 10 % with triptophane, lysine and methionine; and some residual activity with leucine, valine, isoleucine, phenylalanine and arginine. The optimal pH for activity is found between 6.5 and 7.5. The circular dichroism spectrum allowed us to classify the protein as part of the a/b hydrolase family. In the range of pH between 4.5 and 7.5 the protein undergoes structural changes, together with a decrease in thermal stability as can be seen by circular dichroism studies. Inside this pH range the protein precipitates as soon as it begins to denature due to the effect of the temperature, while outside this range the protein denatures but does not precipitate upon heating. Further studies with this aminopeptidase and with others are needed to see if this behavior is exclusive of this protein or is a general feature of this type of proteins. Financial support by  FAPESP and LNLS.