Apparent isocitrate lyase activity in Leishmania amazonensis.

Area of Science:

• Parasitology
• Molecular Biology
• Biochemistry

Background:

• Glyoxylate cycle enzymes, including isocitrate lyase (ICL) and malate synthase (MS), have been reported in Leishmania species.
• However, the genes for ICL and MS are notably absent from current Leishmania genome annotations.
• This discrepancy has led to underestimation of the glyoxylate cycle's significance in these parasites.

Purpose of the Study:

• To re-examine and confirm the presence and activity of isocitrate lyase (ICL) in Leishmania amazonensis promastigotes.
• To characterize the molecular properties and localization of the ICL enzyme in this parasite species.

Main Methods:

• Enzyme activity assays were performed spectrophotometrically on cellular extracts of Leishmania amazonensis promastigotes.
• Zymography was used to visualize protein bands with ICL activity.
• Immunoblotting with antibodies against Bacillus stearothermophilus ICL was employed to identify the specific polypeptide.
• Indirect immunofluorescence microscopy was utilized to determine the subcellular localization of the ICL antigen.

Main Results:

• Spectrophotometric assays and zymograms confirmed apparent isocitrate lyase (ICL) activity in Leishmania amazonensis promastigote extracts.
• Immunoblotting identified a 40 kDa polypeptide exhibiting ICL activity, consistent with the zymogram results.
• Indirect immunofluorescence revealed that the ICL antigen is distributed in both diffused cytoplasmic and punctate aggregate patterns, localized beneath subpellicular microtubules.

Conclusions:

• The study provides clear evidence for the existence of isocitrate lyase (ICL) activity in Leishmania amazonensis promastigotes.
• The identified ICL is a 40 kDa protein with a distinct cytoplasmic localization pattern.
• The findings highlight the potential metabolic relevance of the glyoxylate cycle in Leishmania, despite the lack of gene annotation.