Ornithine decarboxylase of Leishmania donovani: biochemical properties and possible role of N-terminal extension.

Leishmaniasis is a wide spread tropical disease caused by protozoan parasite Leishmania which belongs to order kinetoplastida and family trypanosomatidae. Ornithine decarboxylase is key enzyme in polyamine biosynthesis in Leishmania donovani. Here, we report biochemical characterization of ornithine decarboxylase from L. donovani. Furthermore, we have also investigated the role of N-terminal extension (250 amino acids) found in ornithine decarboxylase of L. donovani (LdODC). The removal of N-terminal extended region of LdODC results in improved stability of the protein. However, the truncated LdODC does not show any activity. Apparently, while N-terminal extended region of LdODC helps in proper folding of the protein for catalytic activity, there is a stability trade-off. The native full length LdODC with N-terminal extension has activity but lower stability. Thus, there is trade off of conformational stability for enzyme activity. Comparison of biochemical properties of both, fulllength and truncated enzymes, have provided interesting insights about the role of N-terminal extension in the protein.