Organization, sequence and stage-specific expression of the phosphoglycerate kinase genes of Leishmania mexicana mexicana

Abstract

In Leishmania mexicana two genes were detected coding for different isoforms of the glycolytic enzyme phosphoglycerate kinase. This situation contrasts with that observed in other Trypanosomatidae ( Trypanosoma brucei, Trypanosoma congolense, Crithidia fasciculata) analyzed previously, which all contain three different genes coding for isoenzymes A, B and C, respectively. All attempts to detect in L. mexicana a type A PGK, or a gene encoding it, proved unsuccesful. We have cloned and characterized the genes PGKB and PGKC. They code for polypeptides of 416 and 478 amino acids with a molecular mass of 45146 and 51318 Da, respectively. The two polypeptides are 99% identical. PGKC is characterized by a 62 residue C-terminal extension with alternating stretches of hydrophobic and charged, mainly positive amino acids. As in other Trypanosomatidae, PGKB is located in the cytosol, PGKC in the glycosomes. However, Leishmania mexicana distinguishes itself from other trypanosomatids by the simultaneous expression of these isoenzymes: ≈80% of PGK activity is found in the cytosol and 20% in the glycosomes, both in promastigotes and in the amastigote-like form of the parasite.